From Pathfinder Adventure: Crown of the Kobold King, which isn't enabled.

Falling Debris

HAZARD 1

Stealth +10

Description A net filled with stones and a small anvil crashes down on someone who steps into the room.

Disable DC 17 Thievery to disarm the trap through a cracked-open door, or Interact to open the door slowly without triggering the trap

Drop Debris

Trigger A creature opens the door without taking care to avoid triggering the trap;

Effect The net drops a dozen hefty stones and a small but quite hard anvil onto the creature, inflicting 3d6 bludgeoning damage (DC 17 basic Reflex). The sound of this trap going off alerts Gurtlekep in area C8.

Pathfinder Adventure: Crown of the Kobold KingOGL