Tow Ready 63228 Trailer Coupler Lock
Your rig is secure when you're out and about with a receiver lock. But what's stopping even a clumsy thief from pulling up to your house at night and hitching your parked trailer to his truck? That's where a coupler lock comes in handy. The lock fits around the coupler, making it impossible to hitch it to anyone's trailer.
Coupler Lock, "Gorilla Guard" for 2" Couplers