If your trailer's hitch is like most, it has a hole that a pin fits through to prevent it from becoming uncoupled during towing. The Dead Bolt Coupler Lock replaces this pin and ensures that your trailer can't be removed form the hitch when you leave your vehicle unattended. This provides an additional level of security when traveling to and from shows and clinics, as well as at the show grounds. When unhitched, you can also use this lock to make it impossible to hitch your trailer to another towing vehicle.