Drawbridge
There are three drawbridges in NetHack - one in the Castle, and the other two on the Valkyrie quest. They are widely considered extremely dangerous due to a persistent myth that when standing directly in line with a drawbridge when it is destroyed, you can be hit by a flying chunk of metal which will kill you instantly. In reality, the only two squares where you are in danger of being hit by flying debris or flying chunks of metal are the portcullis and the drawbridge squares. However, you still don't want to stand directly in line with a drawbridge to prevent foes on the other side from blowing it up with a Wand of striking.
A closed drawbridge is represented by #, and an open one is represented by ..
Commentary
The door beyond the moat of Fort Ludios is not a drawbridge, but an ordinary door.
Strategy
The castle drawbridge is opened by playing the passtune on a musical instrument. The passtune can be given to you by your god while praying on an altar, or derived by playing a game of musical mastermind right in front of the drawbridge.
Once you have the passtune, the drawbridge can be opened and closed at will in one turn, by playing the instrument again. Anything standing on the open drawbridge or on the square the drawbridge moves into when it closes will be crushed or drown, killing it instantly. This is thus an excellent way of clearing out the hordes of monsters in the castle courtyard. Do note however that this will destroy any possessions carried by the monsters you clear out--and the monsters in the castle are an excellent source of loot.
Alternatively, with a decent source of opening and locking (wands or wizard lock + knock are good sources), you can repeatedly open and close it without even knowing the passtune.
Some players prefer to destroy the drawbridge as soon as possible, from a safe distance, to eliminate the chance of a Soldier with a wand of striking hitting it at random and sending the huge chunk of metal flying towards you. In any event, never stand in line with a drawbridge, whether open or closed, in a combat situation. Drawbridge death is irrespective of hit points or armor class.
The drawbridges in the Valkyrie quest
The drawbridges in the Valkyrie quest cannot be opened or closed with the passtune. Other methods still work: a wand of locking or wizard lock spell will close them, while a wand of opening, knock spell, or the Bell of Opening will open them. They are subject to being destroyed by force bolt or a wand of striking, with the same risk of instadeath as the Castle drawbridge.
Reference
dbridge.c contains the source code for handling drawbridges, which runs to some 940 lines--a real tribute to the kind of devotion to minute detail that characterizes NetHack.
This page may need to be updated for the current version of NetHack.
It may contain text specific to NetHack 3.4.3. Information on this page may be out of date.
Editors: After reviewing this page and making necessary edits, please change the {{nethack-343}} tag to the current version's tag or {{noversion}} as appropriate.
