Something important is locked. There is a key. However, this key is inside. You need the key to reach the key.
While this trope can be Played for Laughs with trivial situations such as locking your car keys in the car, many works that use it choose to employ it in a far more dramatic manner. The hero is on a quest to find the key, eventually finding some other way to reach what he needed the key for - and then he finds out that his initial quest was futile; the key was inside all along.
In a video game, this can be used to create a Door to Before.
Subtrope of the Catch-22 Dilemma.
- In one episode of Cardcaptor Sakura, Tomoyo has been trapped in a classroom as Eriol messed with the floor plan as a test for Sakura. Sakura needs to find her, and Syaoran says he has a magical technique that can locate lost people, provided she has left an object behind. (Not unlike a dog using scent, except it works off auras/energy signatures.) Tomoyo did have an umbrella...but it's with her in the very classroom they're trying to locate. The actual solution, which Sakura eventually figured out, was to convert the Shadow card and use its power to seek Tomoyo's shadow, following it as it went.
- In the third episode of Cowboy Bebop this is played straight. The only way to decrypt the special decryption program is with a cypher key that was itself encrypted, and only the protagonists know where the key is.
- Played for Laughs in Yuri Is My Job. The main character, Hime Shiraki, is a girl who wants everyone to love her. She ends up working at a salon where the employees roleplay as members of an all-girls school, and takes part in the Blume elections, in which one student is chosen as "Lady Blume," to represent the school, and is given the privilege of making a decree. Hime considers asking for everyone to love her, but since the Blume title is decided by popular vote, Hime's friend Kanoko thinks, "Hime-chan, that's already what being Lady Blume means!"
- Played for Laughs in Yu Yu Hakusho. At the start of the Chapter Black arc, Kuwabara, Botan and Kurama are searching for Hiei, since Yusuke's been kidnapped and those responsible want the four of them to come to the hideout. After the group realizes that their tools won't help find Hiei, Botan laments that Hiei isn't here, or else he could find himself with his Evil Eye.
- Disney Ducks Comic Universe:
- In the Donald Duck story "Sagmore Springs Hotel", Donald, as a Hotel Manager, accidentally locks the combination to the hotel safe inside the safe. In his attempts to open it, he ends up devastating the entire hotel and destroying his uncle's important cheque.
- Another story had Magica DeSpell tracking down the ingredients for a spell that will enhance her magical abilites to unstoppable levels. After getting run ragged tracking down various rare ingredients, she discovers the last ingredient is... the most prized possession of her worst enemy. Which just happens to be Scrooge McDuck's #1 Dime, and she needs the potion to get the dime in the first place. Poor Magica throws a fit and gives up on making the potion.
- An Achille Talon story has an emergency phone protected behind a glass that must only be broken with a hammer that is also behind the glass. This causes a breakdown to the policeman who wanted to use it, while another character attempts to comfort him by saying it probably prevents a lot of hammer thefts.note
- One strip of The Far Side had a pair of aliens trapped on Earth. As a crowd of curious humans approaches them, one of them says to the other "Well, here they come. You locked the keys inside, you do the talking."
- In the first Back to the Future movie, Marty is thrown into a car trunk by Biff's goons. The car belongs to one of the members of the band that was playing at the dance, who chase them off. The band tries to get Marty out, but the keys are in the trunk. This becomes a plot point later when the band manages to free Marty, but the guitarist slices his hand as he does it, forcing Marty to take over at the dance.
- A similar moment happens in The Whole Ten Yards.
Lazlo: You locked my son in the trunk?
Oz: No! No, sir. He locked himself in the trunk.
Lazlo: [pause] This I believe.
- In the Joss Whedon version of Much Ado About Nothing (2012), Nathan Fillion, playing the fuzz, has this happen to him.
- In the Hugga Bunch Made-for-TV Movie, the villainess, Queen Admira, stays young by eating young berries, which grow on a tree she keeps locked under a glass dome. When the heroine comes to take some young berries for her grandmother, Admira catches her in the act. In her hurry to leave, the heroine accidentally leaves the key for the dome on the ground by the tree, and as the dome descends, Admira lunges toward the key, but is too late.
- In Little Monsters the heroes are trapped in a locked room by the villain. After MacGyvering a way for Maurice to be reduced to a pile of clothes and slid under the door, once on the other side he says:
Maurice: Any of you freaks know how to pick a combination lock?
- Although he's simply joking and opens the door a second later.
- This exchange from Space Balls:
- (Guard shoots the lock on the Winebago)
Dot: Open the door!Barf: I can't, the lock is fused!Vespa: What about this door?Barf: Its locked!Vespa: Where are the keys?Barf: Inside!Vespa: Oh great!
- (Guard shoots the lock on the Winebago)
- Played for Drama in The Bourne Legacy. When one of the scientists locks the door to a top secret lab and starts shooting his colleagues, an armed security guard responds, only to be told that everyone who knows the access code is already in there with the killer. By the time another guard arrives with a master key, everyone's dead except for a Sole Survivor.
- In Up the Chastity Belt, Nick the Pick is called in to unlock Lobelia's chastity belt. However, all of his tools are in his toolbox, which is locked. And he can't find the key. The rest of film shows his increasingly desperate attempts to open the toolbox.
- World War II. Hitler hears of the Staff of Moses, which can make the seas part. If the Germans can get their hands on it, they can invade England by land. Where is the staff? In the British Museum.
- In Blå Tornet, the Guardian has been sleeping on the High Altar for over a thousand years. There are a lot of prophecies about how a chosen one will one day wake him. In the meantime, one of the worst blasphemy someone can do is to touch the Guardian's holy sleeping body. It turns out that they artifact needed to wake the Guardian is in fact inside the altar: Only a blasphemer can heal the horrible wrong that happened so long ago, and lead the civilization back on the quest the creators had originally intended.
- There's a recurring gag in Thief of Time about "opening the box with the crowbar you will find inside". The solution is get some help; in the literal example early on, Igor is inside the box with the crowbar and hands it to Jeremy through the slats.
- In Jingo the Bursar has locked himself in the Unseen University safe and taken the key with him. "It's not even as if there's a keyhole on the inside".
- In Going Postal, Vetinari plays mind games with condemned criminals—if they use the spoon they get with their gruel to try and dig a stone block out of the wall as part of an escape attempt (ruining the spoon in the process), they finally pull the block out only to find a little alcove behind with a shiny new spoon in it.
- Guards! Guards! has an interesting example. Vetinari is locked in the dungeon by Wonse after the dragon becomes King, and when Vimes manages to break in and find him, he realizes that the dungeon has a complicated locking mechanism on the inside so that Vetinari is, at that moment, the safest person in the city. He also, of course, has a key to the dungeon, and promptly uses it once the dragon is defeated.
- A fairly standard situation in the Locked Room Mystery is for the police to have to break into the Locked Room, because the key is inside with the deceased.
- Isaac Asimov:
- Subverted in a short story by Isaac Asimov, where people are searching for an uranium asteroid an illegal miner found, and due to the miners dying in an accident, all they have is a statement by a silicon based alien that the coordinates are "on the asteroid" (the alien died right after saying that). In the end it turns out that the alien wasn't particularly up to date in astronomy, and the coordinates were actually on the ship - hidden among the registration codes of the equipment.
- "Insert Knob A in Hole B": The machine that can correctly put together the components of any device, is disassembled into its components for shipping.
- A Song of Ice and Fire: As it turns out, to solve a prophecy about how to get dragons back into the world so you can be very powerful through controlling them again... you kind of needed to remember enough about how to incubate dragon eggs, first, to understand what the hints in the riddle were likely to be blathering on about to spot which circumstances would help to hatch them successfully. Easy. Not. Some, like Aegon V, tried brute-forcing the thing using overwhelming power (lots of Greek Fire) and some best guesses: it failed. Others might have tried to be sneaky chessmasters (looking at you, Bloodraven) trying to move people and circumstances into likely positions — to then get burned by the unexpected consequences of getting the code a little wrong back-blasting them. Alternatively, you could just totally luck out by hitting on the actual combination randomly without meaning to solve the thing... as Daenarys has. She doesn't seem to even know that a full prophecy exists, although she might still know some of the info it had in it. Problem is, once successfully incubated and hatched, you then also need to, you know, find a way to direct and the control your dragons, since how to train them has also been lost to the mists of time. And, there's only one way to learn, now: playing with fire by trial and error. Which a lot of people will be very unlikely to be willing to let you do, so will have hidden or destroyed pieces of information you would have needed to get to this point in the hopes of stopping you getting to the dragon-riding stage in the first place... Um. No wonder the Targaryens repeatedly hit problems with trying to force that prophecy open with the equivalent of either a crowbar or lockpick...
- Towards the beginning of the Lord Darcy novel "Too Many Magicians", Master Sorceror Sir James Zwinge is in apparent distress in his hotel room. But he'd enchanted the lock to his room so that only one copy of the room key could open the lock - his personal copy, which was with him in the room. The people responding to his call for help had to smash a hole in the door with an ax to get inside, by which time he'd bled to death.
- A variation in Star Corps Agent. The protagonist gets his hands on a box his partner was killed for. He can only guess what's inside. Possibly a way to get advantage in the war with the Radnits. But would it help him get off the hostile planet alive to deliver it to Earth? It could be a powerful handheld weapon that he could use to shoot his way through the spaceport cordon. Or it could be designs for a ship part, which are utterly useless to him at the moment. But the box is of a type that can only be locked from inside, which means that if he opens it, he won't be able to use it to barter for a way off the planet. He ends up opening it anyway and finds a genetically-engineered symbiote that turns him into a Super (normally, Supers are born). He swaps the symbiote in the box for his disguise symbiote, then uses telekinesis to lock the box from the inside. The Radnits scan the box and detect a symbiote, so they let him leave.
- When humanity starts reverse-engineering alien technology in Troy Rising, their Artificial Gravity prototypes are clunky, prone to lethal malfunctions, and flies to pieces under anything but the lighest use. By the time they discuss this with Tyler Vernon, the scientists have worked out that the only tool capable of making an efficient gravity generator is another efficient gravity generator.
- On two separate occasions on I Love Lucy, Lucy gets locked in a meat freezer and a steamer trunk. Both times, she has the key to the lock.
- Corner Gas:
- Hank had a lockbox with a combination lock. One of the things inside the lockbox was a notepad where he wrote down important stuff he needed to remember... such as the combination to the lock.
- Hank once locked his keys in his truck. He had a great deal of difficulty trying to unlock it with a coat hanger, until Davis passed by and notified him that his passenger-side window was open.
- That happens in an episode of Get Smart too, regarding the wall safe in the Chief's office.
Chief: Have you got the new combination, Max?
Max: New combination?
Chief: Yes, according to standard security procedures we changed the combination yesterday. Do you have it?
Max: Well, I didn't memorize it, but I had the usual three copies made.
Chief: Where are they?
Max: I burned them.
Chief: Oh, yes. Of course. Do you have the Master Copy?
Max: No I don't, Chief. But I put it in a place where no one will get it.
Chief: Where, Max?
Max looks at the wall safe.
- In an episode of Caroline in the City, Del and Charlie get trapped in Del's car due to a snow plow and Charlie accidentally locking the keys in the trunk instead of an ice scraper.
- In one episode of the children's magazine show Jigsaw, the cast were given a telephone with which to summon the OO Men for their Once an Episode appearance. The telephone was in a sealed, glass-fronted cabinet, so there was also a hammer to break the glass. The hammer was inside the cabinet.
- Parodied in a 2011 episode of The Colbert Report. While discussing cloud storage, Stephen proclaims he stores all his information in the cloud, including info needed to answer the security questions when forgetting his password to the cloud.
- One episode of Fraggle Rock had Doc and Sprocket acquiring a locked trunk and spending the entire episode trying to get it open. When they finally do, all that's inside is the key.
- An episode of Cheers had Woody trying to install a VCR when someone handed him the instructional video that came with it. Woody of all people incredulously asks, "We hook it up. . .and then we watch the video on how to hook it up?!"
- In the Black Books episode "The Big Lockout" Manny bought a security system. It was very simple, you press 05 to arm it and then when you go out it will lock automatically. And then when you come back in, you punch in the code and the lock will open. Bernard quickly points out the slight problem with this that if the door's locked, he can't get in to punch in the code to open the door. As it turned out, Manny didn't know the code anyway.
- This is basically what makes some deals of Solitaire unwinnable. If the cards onto which you'd need to move a face-up card all happen to be face down behind it, then they might as well be keys on the wrong side of a locked door.
- Likewise, unwinnable layouts in Mahjong Solitaire result when needed tiles are trapped between tiles that can't be accessed without them.
- Similarly, unwinnable games of Freecell, where the cards you need are locked underneath cards you can't move anywhere.
- A common tool in Metroidvania design, for collectible powerups (such as missile pack expansions): put the powerup behind the obstacle that requires that powerup to bypass. Rather than being used for comedy or drama, this has a more practical game-design purpose, which is to prevent the player-character from picking up an item too early but still being able to display it to the player. Basically, you can see it now, but you'll get it later, after you get the first pack of missiles from somewhere else.
- Also combined with Door to Before. The one you can see may be your first, but you can only get to it from the other side by following a long hidden path. Once you have it you can remove the obstacle and be back where you started without having to backtrack the long way.
- Invoked & defied in Quest for Glory V. Your room at the inn has a storage chest, and you can put your room key in it. However, you cannot keep the key there: The narrator will go on about how you "realize your mistake", and the game will automatically make you take your key back. This mechanism is still in place after you install the "mystic magnets" that will let you teleport into your room (without the key) whenever you want to.
- The Legend of Zelda:
- In A Link to the Past, there's one locked treasure chest whose only key, you are told, is inside the chest, and you can never open it. Fortunately you can drag it with you until you find a master lockpicker.
- In A Link to the Past Randomizer, the randomizer logic explicitly averts this; but the more recent versions make an exception for the specific cases where a Small Key is the only thing behind an ordinary lock. Also, in the two dungeons note where the Big Key isn't required to reach the boss (or any other chest), the Big Key can be locked inside the Big Chest, since it doesn't prevent completion of the game.
- Link's Awakening:
- An Unwinnable by Insanity example in Angler Tunnel: the door one particular Interchangeable Antimatter Key was meant to be used on has another behind it, but by making a tricky jump it could be used on a different door that didn't have a replacement behind it.
- Played with in the Key Cavern, also averting Permanently Missable Content. A hub room in one part of the dungeon had four locked doors. Three of them were dead ends that also contained a key (which could be used on one of the remaining locked doors), while the fourth allowed the player to proceed (but did not give the player a key, so the other doors accessible from the hub remained locked). Near the end of the dungeon, an extra key could be obtained to access any locked rooms the player hadn't entered.
- At one point in Skyward Sword, a key is held by a Mook on the other side of some bars. The solution is to use the whip to grab the key.
- In Minish Cap, Talon lost the key to Lon Lon Ranch, and the spare key is inside the house. The solution is to shrink down to Minish size, enter the house through a small hole, pick up the key inside and bring it to him.
- Breath of the Wild:
- The shrine containing the bomb rune is surrounded by walls, and the gate is blocked by a giant rock that can only be destroyed by... bombs. It serves as a reminder to players of previous Zelda games that in this one, just climbing over the wall is a viable option.
- A shrine has a literal example, where a chest containing the key you need to get into a cell is inside the cell. The solution is to shoot a burning arrow through the cell's bars into the chest, which is made of wood. Once the chest burns up, you can use the Magnesis rune to pick up the key.
- The upper reaches of Death Mountain are so hot that Link will catch fire the instant he enters the hot zone, and rapidly start losing health as a direct consequence. Fireproof Elixirs, which negate this effect, can be bought at Eldin Ranch or off of Goron merchants at lower altitudes, but the very nature of the game means you could very well not approach from that direction, and even then the elixirs don't last forever (though one Fireproof Elixir is enough to get you to Goron City, and three will last you long enough to do some exploration in the process). Fireproof Lizards and Smotherwing Butterflies exist to make more elixirs, and Flameguard armor can be bought in Goron City to protect from the extreme heat... and both are found in the ultrahot parts of Death Mountain. You can circle around to approach from the south, or you can cook enough food to feed all of Hyrule and chomp on it until you get to Goron City. As a bonus, the armour merchant freaks out if you talk to him without active flame resistance.
- Similarly, while still on the Isolated Plateau, you need frost resistance to get to one of the shrines. You can either learn how to craft frost resistance food at this early stage, and also receive a frost resistance armor as a reward, or if you can manage to make it all the way to the highest point in the cold zone (by building lots of camp fires along the way, carrying a torch whenever you've got a free hand, and eating food to heal whatever hearts get lost) the Old Man will reward your tenacity with the same piece of armor.
- In Adventure, on the hardest difficulty, the items were distributed in a kind-of-random manner, which occasionally resulted in the gold key being locked in the gold castle. Despite entering the gold castle being a necessary step in completing the game (the last step, in fact), this did not make the game unwinnable, as sooner or later the bat would fly in and take the key out.
- In Zork: Grand Inquisitor, there is a glass box ("In case of adventure, break glass") containing a spell scroll, a sword and a hammer. It can be easily opened, but the clamp holding the sword will not let go. The obvious solution is to open the box, take the hammer, close the box, break glass. Then the clamp lets go and you can take the sword.
- In the NES port of Metal Gear, the keycard required to enter Building No. 4 is inside the building itself. This requires Snake to get captured on purpose in order to get inside said building.
- A similar situation occurs in Snake's Revenge when the player reaches the entrance of the first enemy base. Only this time it's one of Snake's comrades who allows himself to get captured, so that Snake can sneak in undetected.
- The first level of Mystery of Time and Space has the key in the keyhole on the other side of the locked door. To get it, you have to slide a poster underneath the door and then push something small enough through the keyhole to make the key drop onto the poster, which you can then retrieve.
- The Interactive Fiction game Savoir-Faire has one locked door where you can see the key through the keyhole. The solution to unlocking this door is more creative than the usual ones, due to the game world's Functional Magic which lets you "link" similar things to each other so that doing something to one of them will similarly affect the other: link the key to your sword (it's ornate enough to allow the link) and then turn your sword in its sheath. Voila, an unlocked door!
- Starship Titanic has a circular version - in order to obtain a hammer, you need to press a button with a long stick. However, in order to obtain a long stick behind glass, you must break the glass with a hammer. Fortunately, there's a parrot perch that you can use in place of the long stick.
- Ratchet & Clank: Going Commando has a similar circular version. On one planet there is a wrench upgrade in a glass case with a "use wrench to break glass" note attached. Nearby in another glass case there is a rock with a "use rock to break glass to get wrench to break glass to get rock" note. As Clank tries to figure out the puzzle, Ratchet just smashes the wrench's case with his current wrench and takes it.
- BioShock plays this straight early in the game. The head dentist has been killed and thrown through his office window, and the only way to get in is to use the Telekinesis Plasmid to get his key off the wall behind the window.
- Ancient Domains of Mystery: There's an intentionally useless item called the scroll of cure blindness. You can't read scrolls when you're blind. (It has some other, more creative uses, however.)
- In Persona 5, during the infiltration of Madarame's Palace, the group finds a door that is guarded by a laser barrier, and a sign helpfully points out that the laser beams can be disabled in a control room on the other side of the barrier. Luckily, they have a way to get in: since the door matches one in the real Madarame's house, Morgana picks the lock so that Madarame witnesses it being opened, thereby changing his cognition that the door is unopenable and resulting in it being opened in the Metaverse. At that point, the protagonist and Ryuji take advantage of the window of opportunity to go inside and reach the control center so they can deactivate the beams.
- From a gameplay perspective, the only way to unlock the ability to read two chapters at once requires a lot of effort. You need to unlock Jinbocho, and purchase and read "Master Swordsman," "Call Me Chief," and "Reckless Casanova" (which are the only books that take three sessions each to read) before you can buy the "Speed Reading" book. Once you read that book, you can read all the others in one night, but since all other books require one or two sessions to read without the book, this ends up being an Awesome, but Impractical perk.
- Dwarf Fortress: Embarking without an anvil walks the line between Self-Imposed Challenge and Unwinnable by Insanity. You need an anvil to forge anything out of metal, and anvils can't be made out of anything else.
- Paper Mario: When you first meet Bombette, she is locked up in the dungeon at Koopa Bros. Fortress. As there is no door to the cell, you need to travel to the floor above and trigger a trapdoor that will drop you into the cell. Fortunately, Bombette will join your party at this point, and you can use her ability to blast through the wall. Bombette will then realize that she could broken out sooner if she had actually thought to do so.
- Banjo-Tooie: When you first enter Grunty Industries, the front door to the factory will be locked, preventing you from making any significant progress in the level. However, if you search around a bit, you'll find the switch that opens up the factory's train station. While the station is inside of the locked building, you can leave the level, backtrack to another train station, then ride the train into the station inside Grunty Industries. As you explore the factory, you'll eventually be able to open the front door from the inside.
- When The Angry Video Game Nerd needs to open the plastic case around a Tiger Electronics wristwatch game, he gets a pair of scissors from the Bullshit Man, who complains about needing a second pair of scissors to open the plastic packaging around the first pair.
- Averted in Stuart Ashen's review of the Packbuster (a multitool for opening the packaging around products). The blister pack has a notch cut into one corner so you can open it without using scissors or the Packbuster. As Stuart puts it: "Extra bonus points for that; that is good. There's nothing like buying some sort of device for packages and not being able to get in the package."
- Rinkworks Computer Stupidities:
- A computer teacher plans to hold a class on routers and requests a half dozen from a colleague. The routers are shipped in a pair of cargo boxes secured by combination locks. The page with the combinations is inside one of the boxes.
- A user tries to sign up with an Internet Service Provider, only to discover that access to that ISP's website to set up the account requires a username and password from that ISP. In other words, you need to be a member to access the site to become a member.
- Zoë's first line in Sluggy Freelance is "Help! I need a phone! I locked my keys in the car with the engine running!" This is also referenced later when she temporarily moves to a place with normal people. (Oh, and Clem.)
- In Goblins, the Key of Darkness is inside the locked Well of Darkness because the adventurer who carried it in was killed by a trap.
- Subverted in Tower of God, episode 295: the Ten Bosses of the Name Hunt Station are trying to keep the protagonists from finding a certain key by having one of their number keep it hidden in a room that can only be opened with the same key. It turns out that that part doesn't really matter, though, since the room can't be locked from the inside.
- Darths & Droids In episode 1643, Jim — a player known for plans that he thinks are brilliant — has his character suggest a method of finding the planet Toprawa that ultimately hinges on raiding the Imperial data facility... which is on Toprawa.
- Parodied in the Family Guy episode "Petarded", where a flashback shows one incident where Peter locked his keys outside his car, trapping himself inside.
- In one version of the backstory for He-Man and the Masters of the Universe (1983), Prince Adam was questing with Teela for what would later become his magic sword. Wielding this sword was the only way to enter Castle Grayskull. And yes, the sword was inside the castle.
- In a cartoon episode of Lucky Luke, the usual criminal Dalton Brothers were trying to be honest, and to have a honest work, they open their own bank. At one point Averell Dalton is commanded to open the safe, but he can't remember where the key is, so he opens the safe with dynamite. It turns out that the key is inside, and Averell closed it in there "for safety". Joe Dalton is not amused.
- In What's with Andy? episode "The Great American Lock-In", Andy reverses the locks in the front doors of his school, then lures in Lik and Leech. Unfortunately, he has dropped the keys outside of the school.
- In the Star vs. the Forces of Evil episode "My New Wand", Star's wand goes crazy and seals itself in her closet along with the spellbook. Since Star unlocks the closet with the wand, this presents a problem. She has to learn to channel magic without the wand's help to solve the problem.
- In one episode of Phineas and Ferb, Dr. Doofenshmirtz finds the door to his truck won't close. He spends sometime struggling with the door, finally gets it shut and locked, and then looks in through the window:
Doofenshmirtz: "Those are my keys, aren't they?"
- Played in The Simpsons episode "Marge Vs The Monorail, where a scientist said to Marge the monorail "better to have a damn good conductor". Gilligan Cut to Homer trying to pry open the monorail's cockpit door because he locked his keys in there.
Homer (to Bart): Get a rock.
- In The Raccoons episode "The Intruders!", Cedric and Ralph accidentally get locked inside of Cyril's vault, which is programmed to not open up until Groundhog Day. Cyril points out that there is a key that Cedric can use that can override the system, which is locked in a safe within the vault. Or at least there would have been, if the pigs had actually bothered to put it there...
- This trope is possible for anybody who keeps the passcode to unlock their mobile device in a writing app within the device itself.
- The doors of many apartments and hotel rooms behave like most padlocks: The key isn't necessary to lock them (simply closing them is enough), making it very easy to lock the keys inside. Dorm rooms as well, as many a college student who forgot his key when he goes to take a shower can attest to.
- Many cars avert this by making the front doors require the key to be locked from the outside (by disabling the "lock while open" feature). One can still lock self out using the back doors, but you'd almost certainly have to be doing it on purpose. It's also worth nothing that this and similar safeguards came about because locking your keys in the car was such a pervasive issue. It may be largely averted now, but that's a relatively recent development. However, it can still be possible to manually lock the door by pushing the lock post down, even if the electric lock will unlock the door. And sometimes it will only prevent locking if the key is in the ignition, but not if it's sitting in the seat.
- In his memoir Carrying The Fire, Apollo 11 astronaut Michael Collins devotes some time to explaining why good cockpit design is important. He describes an example of bad cockpit design: there used to be an Air Force trainer with a placard mounted on the canopy rail that listed all the steps of the ejection procedure. Unfortunately, the first item on the list was jettison the canopy.
- Many trains in Great Britain are provided with little hammers that have a notice saying that in the event of an emergency, the hammer should be used to break the windows of the train. The little hammer is always in a little box with a transparent cover and no way of opening the box or breaking into it. Many travelers have wondered how they are supposed to break the glass to get the hammer that allows them to break glass.note
- Even more extreme variation in some Mexican cities: the hammer needed to break the glass is actually outside the glass box... covered by a metal case that's screwed to the wall.