The Universal Trigger Lock is a simple and effective lock that fits most handguns or revolvers. To install, place one side of the trigger lock on one side of the trigger with the post behind the trigger and the second on the other, then use the included key tool to secure the security screw into the lock. Once seated, the security screw sits flush with the surface of the lock. For use with triggers that are toward the rear or middle of the trigger guard, and not for use with lever action rifles.