A Doll's House trap doors:

 

Trap doors are found in the floors.

They will open when you step on them making you fall down to the floor below, or further down if there is another trap door on the same spot on the floor below.

Falling down a trap door will not harm the player in itself. An exception to this is the water trap.

After the player has acquired the wand the trap doors will no longer open.

Trap doors appear in episode 11+.