A detachable lock with a U-shaped bar hinged at one end. It's designed to be passed through the staple of a hasp or a link in a chain and then snapped shut.
"Zombies of people who discovered the pleasure of hurting oneself. They open holes in their body and stick locks in them, and even as zombies they still apparently derive pleasure from inflicting pain on themselves. Lost in their ecstasy, they attack all who would disturb their enjoyment."