Abstract: Two generally flat, circular plates, one having an attached threaded male cylindrical shaped extension and the other an attached mating threaded female cylindrical shaped extension are threaded together through the ring of a trailer hitch tongue until the plates are in contact with the ring and held locked in threaded engagement by a latch to prevent the unauthorized use of the trailer. The latch is spring loaded and is extended through an opening in the side of the male cylinder to engage any one of a number of internal grooves coaxial with the cylinder, cut in the female cylinder, to provide the locking function. A single lobe cam contained within the male cylinder is mounted on the end of a conventional lock cylinder which, in turn, is rotated by a matching key.

Abstract: An anti-theft device secured by sliding the device over a ball-connector type trailer hitch which automatically engages the hitch by means of a spring loaded bolt, to obstruct access by the ball and prevent unauthorized use of the trailer. The device is removed by retracting the bolt using only a conventional key. No tools or auxiliary parts are required to attach or remove this device.