A way to get someone who is locked up inside their home or other shelter. You pour fuel in through the mail slot in the door, or some other convenient opening, and then follow it with an ignition source, such as a flaming rag. Your victim will now find themselves trapped in a House Fire that they have locked themselves inside.
Needless to say, this is a technique that has been employed in Real Life.
- In The Dirty Dozen, the Dozen kill the Nazi bigwigs at the chateau by pouring fuel down the ventilator shaft into the bunker and then igniting it with grenades.
- Money Train has a psychopath pour gasoline through the exchange slot of a token booth, soaking the attendant and the compartment's interior. The psycho then demands all the cash while thumbing a lighter. He gets the loot, then ignites the booth anyway, For the Evulz.
- In The Losers, the Losers hijack an armoured car full of cash. They dump gasoline through the ventilator, dousing the guard and the cash. They then open the door and point out to the guard that if he fires, he will set both himself and the cash on fire.
- In a possible unintentional case in Big Eyes, at one point, Margaret locks herself into her painting room. Walter starts tossing lit matches in through the keyhole. In his defense, he may not have known there was a bottle of highly flammable turpentine right there. Fortunately, it does not ignite.
- Firestorm (1998): When Jesse and Karge are fighting inside the trading post, Shaye bars the doors and soaks the outside in gasoline. He smashes a small window, passes the fuel hose inside and tosses in a flare in an attempt to dispose of both of them.
- In Kittyhawk Down by Garry Disher, Inspector Hal Challis of the Homicide Squad has to look into the killing of an unidentified corpse fished from the sea, as well as searching for a missing toddler and trying to find out who is stealing cars and torching them, and then there's a more mundane letterbox arsonist.
- When the New York City Subway starts using bulletproof ticket booths, Burke notes that any ex-con knows how to get round that; by using this trope and waiting for the ticket-seller to open the booth for you. One ticket-seller couldn't get the door open in time.
- Midsomer Murders: In "Murder of Innocence", a murder is attempted by pouring petrol through the letterbox of a cottage and following it with a flaming rag.
- Rizzoli & Isles: In "Phoenix Rising", this how the killer starts the fire. This turns out to be Murder by Mistake as his actual target lived next door.
- Simon from Misfits did this to the house of a boy who had been bullying him at school, but had a sudden change of heart when he realized it would burn an innocent cat alive, and with no other means to put out the fire, he peed through the mail slot to put it out. He was caught and sent to a psychiatric unit until they determined he wasn't crazy and sentenced him to community service, setting in motion the events of the first episode.
- On an episode of Coronation Street, Loan Shark Rick Neelan shoves a burning newspaper through someone's letterbox: a scene that evoked complaints, claiming that the scene encouraged crime.
- The Bill:
- In "Initative", Garfield and Young investigate when fireworks are shoved through a woman's letterbox.
- In "Fire", an attempt is made on June Ackland's life by pouring petrol through her letterbox and lighting it.
- DCI Banks: Fuel and fireworks dumped through a letterbox are used to start a fatal house fire in "What Will Survive''.
- The New Avengers: A variant occurs in "Complex". When Purdey is trapped inside a building that is trying to kill her, Steed and Gambit alert her that she needs to trigger the sprinkler system by dumping a large quantity of matches and lighters into the mail chute, which is the only access the AI cannot seal off. Purdey uses a lighter to set off the sprinkler and destroy the computer.
- One episode of Mike Hammer (originally a Mickey Spillane book series) has an extortion racket demand "protection fees" against arson. Those that don't pay have hydrogen gas pumped into their heating oil intake, where it seeps out, filling the workspaces. The ignition source is the ringer relay on the rotary-dial telephones.
- Firefighters from Engine 51 of Emergency! responded to a small fire in a house's toilet, and got a horrible surprise when their hoses actually fed the flames! While using dry foam and tarps to combat the fires, the Fire Chief and the paramedics traced the hydrant lines back to a street worksite, where natural gas monkeys were using municipal water lines to flush a gas line.
Fire Chief: You guys ever hear of a check valve?
Gas monkey: Don't need it. [Gas] line pressure's only 200.
Fire Chief: And a hydrant line's only 80.
- Agatha Raisin: Used to torch James' cottage in "Agatha Raisin and the Murderous Marriage".
- New Tricks: In "Prodigal Sons", Sasha and Steve arrive at a suspect's flat only to discover it is on fire. It is later discovered was started by someone pouring acetone through the letterbox and setting it alight.
- Endeavour: In "Cartouche", a house occupied by Kenyan Asians is torched by racists pouring petrol through the letterbox and igniting it.
- A variant occurs in the Call of Cthulhu supplement Terror from the Stars, insert "Field Manual of the Theron Marks Society". One of the tactics described in the manual was pouring oil so that it flowed under a door, then lighting it so it burned the animated mummies on the other side of the door.