A standard trick of the Locked Room Mystery, in which a key must be retrieved from the other side of a locked door. Fortunately, someone left the key in the old-fashioned lock, from which the key can be dislodged with a handy slender tool (icepick, wire, knitting needle), to be caught on a piece of paper slid under the ill-fitting door.
Modern locks are constructed to prevent this, and modern doors' thresholds seldom have sufficient space to do it. Many doors - even in really old houses, depending on architecture - also have doorframes, which make this an outright impossibility. It's also possible for the key to bounce off the paper. Therefore, it's normally used only in period pieces, or stories set in older houses that haven't been renovated in ages.
It is rarely (if ever) mentioned that this trick is only possible if the key happens to be the right way up in the lock, enabling it to be pushed out.
- Boule et Bill once did this, using Bill's ear as the paper.
- In Heroic Trio, two of the protagonists are locked in a storage closet in a hospital as an Ax-Crazy killer sneaks off the maternity ward to kill babies. They managed to hit the door hard enough to dislodge the key on the other side and slip a hand under the door to get it. This scene is an odd 20 Minutes into the Future example.
- Used by the faerie creatures in Don't be Afraid of the Dark. Unusually, this example shows the key landing on some drawing paper from the locked side of the door, so the creatures themselves can stay hidden from the audience until a later Jump Scare.
- In The Window, Tommy manages to unlock the door to his room by pushing the key out the other side and then snatching it with a hanger underneath the door.
- Played with in Alone, where Jess attempts to escape from the basement with this, but the key is stuck in the lock. She notices a bare nail sticking out of a wooden post, pries it out, and uses it to poke the key loose and catch it with her sweatshirt.
- In The Unadulterated Cat by Terry Pratchett, Sir Terry describes doing this to rescue next-door's gerbils from his cat, based on a vague memory of a "beat the burglar" piece in The Eagle, and being amazed when it actually worked.
- Moist tries this in Making Money (he would, being a mostly reformed criminal) but it doesn't work.
- Most Enid Blyton series include this at least once, especially The Secret Seven and The Famous Five.
- Bod escapes from the back room of the antique shop this way in The Graveyard Book.
- Mary Russell: Holmes does this to gain access to Mary's locked bedroom in A Monstrous Regiment of Women.
- In the childrens series The Baker Street Irregulars by Terrance Dicks (involving modern-day Sherlock Holmes fans who solved crimes), a Snooping Little Kid is locked in a room by a suspect, and uses this method only to find someone standing guard outside the door watching the entire process. Fortunately the guard finds it Actually Pretty Funny and lets him escape.
- In The Borrowers, six-inch tall Arrietty tells a human-sized boy to push the key out of the lock, after he has been locked in the nursery by Mrs Driver. Arrietty then pushes the key under the door to him.
- An expanded version is used in an episode of The Mentalist: Not only does Jane retrieve the key this way, but he pulls it back into the keyhole from outside the door using fishing line.
- Happy Days: Richie, Potsie and Ralph are locked in the hall closet by a burglar robbing the Cunningham house, and use this to get out.
- The title character of MacGyver has done this on several occasions.
- Get Smart: Maxwell attempts this in "The Return of the Ancient Mariner", but because he's in a comedy series (and also incompetent) the key falls off and ends up on the floor outside.
- Doctor Who:
- Used perfectly straight in the classic episode "The Talons of Weng-Chiang". Bizarrely, the British Board of Film Classification objected to this scene when they vetted the VHS release, because it was teaching children criminal skills. The director pointed out that the concept was used by Enid Blyton, and his own experience was it didn't even work, so the BBFC relented.
- Used again in "The Woman Who Lived", set in the 1600s. The Doctor was going to sonic the lock open, but Ashildr beat him to the punch. Using one of her own Wanted Posters, no less.
- Colditz After finding the door locked and the window barred, Dick Player easily manages to bring the key to his side of the door using method. 
- The Coroner: Done by the family of the Victim of the Week to enter the room where the murder has occurred at the start of "Napoleon's Violin". In this case, it is an old, un-renovated stately home.
- Father Brown. Father Brown faces a locked door and asks for a hatpin: as an antique model, the key was left in the keyhole on the far side of the door, and he's able to poke it out and pull it under the door on a sheet of paper. Mrs. McCarthy looks slightly disappointed, apparently assuming he was going to use a Hairpin Lockpick.
- Dead Man's Gun: In "Death Warrant", Pike gains access to Joe Rule's hotel room by sliding a "Wanted!" Poster under the door and using his dagger to poke the key out of the lock on to the poster and drawing it back under door.
- The Odd Couple: Oscar does this when he's locked in the closet for some reason.
- Used with no modification in Zork II.
- Played straight in Dark Fall The Journal.
- Subverted in Scratches, in which the key lands on the paper but is too large to fit under the door. Micheal even lampshades the trope as that happens.
- One of the early puzzles in Mystery of Time and Space.
- Used as the solution to a puzzle in Simon the Sorcerer, when Simon finds himself locked inside a pantry.
- This is one of the first puzzles in the Crimson Room series of You Wake Up in a Room Flash games. Although unlocking that door only lets you into another locked room, this one more secure.
- Used in Alone in the Dark 2 by Carnby to get into the underground wine cellar.
- This is one of two ways to get into the murder room in Post Mortem. The other involves regular lock-picking.
- This shows up in prison with Zork: Grand Inquisitor. Though the genre savvy jailors didn't include a lock on your cell door, so you need first to cast a spell to create the lock and the key in the first place...
- Very common in inventory-based casual adventure games.
- You do this while playing as Nico on the second visit to the murdered hacker's apartment in Broken Sword: The Sleeping Dragon using her pencil and a handy nearby newspaper (the first time you climbed onto the balcony and opened the latch on a window with her press ID card).
- One of the least-original challenges in Escape the Museum is this.
- This is used to get into one room fairly late in Penumbra: Overture, though bizarrely the room it's done in seems relatively modern.
- Discussed in Leisure Suit Larry 1: In the Land of the Lounge Lizards Reloaded, as seen in the page quote. Note that the door Larry was talking about was a sliding door, so it wouldn't have worked anyway.
- One escape from the Botanica casual game series uses this method. Paper isn't necessary, as the key falls on a floor mat already protruding under the (very ill-fitting) door.
- Subverted in the second Nightmare Realm hidden object game, as the key falls through a crack in the floor while it's being drawn under the door.
- Used in Hugo II: Whodunit? to have Hugo escape a locked laundry. The review of the game in PC Gamer's "Saturday Crapshoot" has the reviewer breaking into a raging rant about how cliche and unrealistic this puzzle is.
- Optional in Phantasmagoria to get into the attic. If you forget to put the paper down, you can just use the fireplace poker to retrieve the key, instead.
- The trope was discussed in a magazine article promoting Full Throttle, by comparing how that game's protagonist, Ben, would open a locked door using a sandwich compared to Bernard Bernoulli from the Maniac Mansion games. Bernard would disassemble the sandwich to use the lettuce and toothpick, according to the trope. Ben would simply eat the sandwich and kick the door in.
- Escape from the very first room in the IHOG Sacra Terra: Angelic Night is achieved via this method.
- Another IHOG example appears in Shiver: Vanishing Hitchhiker as the means of escape from the hospital's morgue.
- Played straight with a newspaper and screwdriver in the bonus game for Redemption Cemetery: Embodiment of Evil.
- If Valdo gets captured trying to move around Cloux Manor in the final act of Secrets of da Vinci: The Forbidden Manuscript, he has to utilize this to get out of his locked bedroom. The game makes a point of hiding a sheet of paper in the room for him to use in case there isn't one in his inventory.
- Explicitly mentioned to be Yahtzee's measure of a good adventure game in his Zack & Wiki review.
- The featured puzzle in day 2 of Oedipus in my Inventory.
- Used in a parody of Jurassic Park on The Critic, when a velociraptor uses this technique to open a door, demonstrating its intelligence. It then dons an evening jacket and pipe as it explains its plans.