# Trap door

^ trap door 

Generates

levels with diggable floors, closets, Castle

Effect

Fall to lower level

A trap door is a type of trap that appears in NetHack. It is somewhat identical to a hole: it drops any monster that steps on it to a deeper dungeon level, though it starts out hidden.

Contents

1 Generation
2 Description
3 Removal
4 Strategy
5 History
6 Messages
7 Variants

7.1 SLASH'EM

7.1.1 Messages

7.2 UnNetHack
7.3 EvilHack

8 Encyclopedia entry
9 References

Generation
Trap doors can be randomly generated at any dungeon level, but cannot be generated randomly beneath boulders or on levels with non-diggable floors such as the vibrating square level - the Castle has five statically placed trap doors that are the only entrances to the Valley of the Dead. If a trap door would be randomly generated on a level with a non-diggable floor, it is replaced with a falling rock trap.
Trap doors are sometimes found in closets, with the engraving "Vlad was here" in front of the door.
If you kick a throne and do not destroy it or knock loose treasure, there is a 1⁄4 chance of a trap door suddenly appearing; it cannot be triggered any other way, and will close up as soon as you land.

Description
Main article: Hole § Effects
You or another monster that steps on a trap door will fall at least one dungeon level.[1][2] As with holes, there is no upper limit, and you cannot fall beyond the Castle. It is common to fall 2 or 3 floors if you trigger a trap door, while monsters never fall more than one floor.[3][4] Pets and monsters with the follower attribute that are on an adjacent square when you fall through a trap door will follow you down to whatever floor you land on.
Pets that fall through a trap door while leashed lose a point of tameness, and the leash is removed. Monsters that levitate, fly or are at least huge size cannot fall through trap doors, including you if you are levitating or in an applicable monster form - while flying above a trap door, you can press &gt; to swoop down through it.
Zapping a wand of opening or the spell of knock at a trap door's position will trigger the trap and reveal it.[5] Zapping a wand of locking or the spell of wizard lock at a hole will turn it into a trap door.[6] Zapping a wand of striking at a trap door below you will destroy it and turn it into a hole.[7]

Removal
A trap door can be removed by pushing a boulder into it, or by zapping a wand of locking or the spell of wizard lock at it.

Strategy
Known trap doors can be a useful escape for you in a pinch.

History
Trap doors first appear in Hack 1.0.
In NetHack 3.4.3, earlier versions and some variants based on those versions, plugging all of the Castle trap doors is a bad idea, as the only other way to access the Valley of the Dead is via branchport or a levelport with teleport control; in the event plugging them is deemed necessary, players would always leave at least one open. As of NetHack 3.6.0, the squares containing the trap doors can be dug out if they are filled.
The ability to fly freely down trap doors was added in NetHack 3.6.4.

Messages
A trap door opens up under you!
You activated a trap door.
Some dust swirls beneath you.
An unseen hole was transformed into a trap door.
The trapdoor beneath you shatters.
You destroyed a trap door with a wand of striking, turning it into a hole.
There's a trapdoor beneath you; it shatters.
As above, but the trap door was hidden.
You fall down a shaft!
You fell 2 levels.
You fall down a deep shaft!
You fell 3 levels.
You fall down a very deep shaft!
You fell 4+ levels.
Variants
SLASH'EM
In SLASH'EM, an Archeologist wielding a bullwhip will not fall through trap doors, though objects on that square may still fall through.[8]

Messages
But thanks to your trusty whip ... You don't fall in.
A trap door opened under you, but you were an Archeologist wielding a bullwhip, preventing you from falling through.
UnNetHack
In UnNetHack, the new Castle layouts have different trap door counts and placements: nine trap doors appear on the "island" map, while three appear on the "river" map.

EvilHack
EvilHack uses the same possible layouts for the Castle as UnNetHack above, though the river of water in the second map is replaced by lava.

Encyclopedia entry

I knew my Erik too well to feel at all comfortable on jumping into his house.  I knew what he had made of a certain palace at Mazenderan.  From being the most honest building conceivable, he soon turned it into a house of the very devil, where you could not utter a word but it was overheard or repeated by an echo. With his trap-doors the monster was responsible for endless tragedies of all kinds.

[ The Phantom of the Opera, by Gaston Leroux ] 

References

↑ src/trap.c in NetHack 3.6.6, line 1292

↑ src/trap.c in NetHack 3.6.6, line 2478

↑ include/trap.h in NetHack 3.6.6, line 87

↑ src/teleport.h in NetHack 3.6.6, line 1363

↑ src/zap.c in NetHack 3.6.6, line 2494

↑ src/zap.c in NetHack 3.6.6, line 2909

↑ src/zap.c in NetHack 3.6.6, line 2894

↑ trap.c in SLASH'EM_0.0.7E7F2, line 359