I guess it would be more of a “trick” than a trap.
Sliding pit trap that drops somebody down to a lower dungeon level.
I ended up rolling several of them when I made my first dungeon after coming back to RPGs in 2010. (I posted the map of Level One for Day 12.)
The way I wrote them up, you don’t even take more than 1 HP of damage, but you end up coming out of a chute, and probably prone on the floor.
Made the walls of the chute very slippery so even a thief would find it a challenge to climb back up.
Sometimes the lid of the pit trap closes and locks so you can’t reopen it from inside.
Did I mention that the noise of you hitting the bottom means a Wandering Monster Check?
Wonder how many levels you fell?
Better hope somebody is left above who has a rope, if they can get the lid open at all.
Or maybe invite everybody down; the loot is probably better down here.
The other alternative is to frantically search for a way to get back up to a higher level.