If you or a monster (see below) step on to a hole and fail to escape it, or an item is thrown onto the same square as a hole, it will fall a random number of dungeon levels, with increasingly less chance of higher numbers of levels. A pet that is leashed to you may be dragged after you, with a chance that the leash may break and the pet remains on the level with the hole.
The falling object will always remain in the same dungeon branch as the hole. Note that this random calculation happens for each turn - even if the same hole is used on the very next action (even if it is the same turn due to having intrinsic or extrinsic speed), the dungeon level calculated may be different.
Once the random number of levels has been calculated, the falling object is placed randomly on the level and any objects that fell in as part of the same turn are placed nearby. Normal room-and-corridor levels will always place falling objects in a valid room.
If you are flying over a hole or a trapdoor and use the > (descend) command, you will always go down exactly one dungeon level. It's also the case when you fall down a hole you've just dug.
Some dungeon levels are made of hard material of which the floor is undiggable, with a message to that effect. Some of these levels will, however, let you create a pit (see below) but not a hole.
Holes in Sokoban, only possible on levels 2, 3 or 4, are special. These holes have air currents that will pull you into them even if you are flying, jumping or levitating over them. The only way to circumvent a hole in Sokoban without filling it with a boulder is to throw an iron ball over the hole. This carries a Luck penalty.
Fast creation of holesEdit
Slow creation of holesEdit
You can dig downward with a pick-axe or dwarvish mattock to make a hole, but this process is very slow and not useful for escaping monsters. The first time you dig downward you create a pit - as you are digging it, you do not fall in, important for those with cockatrice corpses in their posession. Beware, however, that items on the adjacent squares may fall in the pit.
If the level allows you to and you again dig downwards, the pit becomes a hole and any items on the square will fall through to the same random level as you.
Sometimes a monster will intentionally jump into an existing hole to escape. If a monster has a wand of digging, it might zap it downward as well to create a hole, especially if it is damaged. This can be annoying; whenever you find that dwarf (for example), it makes another hole, and when you finally kill it, the wand can be empty. Monsters with digging tools will not create pits or dig downwards if in a pit to escape.
Creatures of size "huge" or larger will not fit into holes or pits and can walk across them. Flying creatures can also traverse holes.