Shitdisk
A frozen disk of whatever is left in your fridge about 1/2" in height so to able to slide underneath a door. When slid underneath it will melt creating a molten pile of shit behind the door, hopefully in someone's path.
Janie slid a shitdisk underneath Jessica's door because she was a bitch. Jessica found a pile of shit in her room in the morning even though her door was locked.