Abstract: A freely pivoting lock ball fits within a trailer hitch ball receiver. A top lock shaft on the ball extends up through a hole in the top of the ball receiver into a lock collar welded to the top of the ball receiver. A cylinder lock fits into a top opening in the lock collar over the lock shaft to lock the lock ball within the ball receiver to prevent theft by towing the trailer with a conventional towing hitch ball. The cylinder lock and lock ball spin freely within the ball receiver and collar to prevent drilling or sawing the lock. There is no room between the cylinder lock and collar or between the ball lock and ball receiver to pry them loose. The lock collar is too thick for cutting with a bolt cutter.

Abstract: A freely pivoting lock ball fits within a trailer hitch ball receiver. A top lock shaft on the ball extends up through a hole in the top of the ball receiver into a lock collar welded to the top of the ball receiver. A cylinder lock fits into a top opening in the lock collar over the lock shaft to lock the lock ball within the ball receiver to prevent theft by towing the trailer with a conventional towing hitch ball. The cylinder lock and lock ball spin freely within the ball receiver and collar to prevent drilling or sawing the lock. There is no room between the cylinder lock and collar or between the ball lock and ball receiver to pry them loose. The lock collar is too thick for cutting with a bolt cutter.