Toppling Door (5e Trap)
From D&D Wiki
Trap Type: Mechanical.
The toppling door is a door with no hinges, that instead opens by falling forward onto anyone unfortunate enough to be caught under their immense bulk. Most toppling doors are massive gates, 10ft wide and 15ft high, constructed from heavy metals such as iron and copper, to ensure the total death of anyone they land upon.
Toppling doors are unique in that they don't seem to have any sort of external triggering mechanism, instead falling automatically when a creature ends its turn within the door's area of attack. A DC(18) perception check can successfully divine that the door is suspiciously lacking hinges or any supporting structure.
The door's area of effect covers a 15ft cone in front of itself. When activated, all creatures within this area must make a DC(14) dexterity saving throw, moving out of the area on a success. On a failure, a creature takes 5d12 bludgeoning damage, is knocked prone, and is restrained under the weight of the door. A restrained creature can escape with a successful DC(17) strength saving throw.