When The Thirty-Six Stratagems talked about removing the ladder once the enemy ascends to the roof, this probably isn't what they meant.
This is an occurrence that shows up very often in Comedy or Action films. A character chases after another, until the chase leads to climbing up a ladder. However, when The Hero gets to the top of the ladder and his enemy starts climbing, the good guy will then push the ladder back, causing it to fall backwards with his enemy still on the ladder.
- One Piece: Zoro does this to some bounty hunters at Whisky Peak.
- In The Smurfs comic book story "King Smurf" (and its Animated Adaptation), the rebel Smurfs attempt to break through King Smurf's defenses by climbing up a ladder, but King Smurf's forces douse the ladder with glue, causing the rebels to get their hands and feet stuck on the ladder long enough to get tipped over. In the Animated Adaptation, though, the glued ladder also rips a hole in the fence, allowing the rebels to get inside.
- The Aristocats: O'Malley does this to Edgar, but it's subverted that while O'Malley does successfully push the ladder back, he winds up falling with Edgar.
- In the climax of Moonraker, Jaws, upon his HeelFace Turn, contributes to the final battle by pushing over a ladder one of Drax's mooks is using to climb towards James.
- In the Richie Rich film, Richie does this to Lawrence Van Dough during the film's climax.
- Robin Hood: Prince of Thieves: Will Scarlet does this to one of the Celts that invade Sherwood Forest.
- There was a scene in Animal House wherein Bluto, the frat boy of Delta House, climbs a ladder to peek in as the sorority girls undress. Suddenly, the ladder tips back (implied to be pushed away from the wall by a certain anatomical reaction on the part of Bluto).
- During the climax of Outlaw Brothers, the Action Girl protagonist takes out a mook while on a higher platform by knocking over the ladder said mook was climbing up towards her.
- In the Shaw Brothers wuxia film The Long Chase, protagonist Kou-ying had to scale a tall ladder to reach his girlfriend, a Damsel in Distress trapped on top of a three-story tower. Enemy mooks tries to force Kou-ying into crashing by pushing the ladder over, and Kou-ying barely escapes with his life in the process.
- An obvious siege example occurs in the film of The Lord of the Rings: The Two Towers during the Battle of Helm's Deep, when Legolas shoots the rope that's being used to raise a ladder with dozens of orcs already on it, and it falls back onto dozens more orcs on the ground.
- The Mummy (1999) opens with an accidental example of this trope leading to some unusually literal Disaster Dominoes.
- Occurs during the market chase scene in Zorro (1975), when Zorro knocks over a ladder to take out two soldiers pursuing him.
- In A Darkness at Sethanon, Moredhel attackers who are climbing up the walls in ladders are simply pushed away.
- Jonny Quest: In "The Curse of Anubis", a bad guy is climbing up a ladder to get to Hadji, who's on top of a building. Jonny appears at a window lower down and pushes the ladder, causing it (and the bad guy) to fall. The bad guy ends up in a water trough.
- On one Wile E Coyote And The Roadrunner cartoon, Wile E. scores a ladder and lays it across a gorge, hoping to trick the Roadrunner into crossing it and falling to his doom. Then he spots the Roadrunner on a cliff overhead and decides to use the ladder to get up to him, with predictable results.
- An episode of Family Guy has a scene where pedophile Herbert peeks on Chris through his window before falling back, a direct parody of the Animal House scene mentioned above.
- The Flintstones: In "The Swimming Pool", Barney, who is feuding with Fred, comes to the Flintstone house to take back a ladder that Fred "borrowed" from him. He swipes the ladder while Fred is using it, causing him to fall onto the ground.
Fred: YOU DID THAT ON PURPOSE!
- One of the weapons of war proposed by Leonardo da Vinci was a device that could push scaling ladders away from the wall of a castle. It resembled a horizontal beam inset into the castle ramparts that could be pushed out suddenly on levers.