This is a lock component that can be part of any locking device that latches as the door closes. In addition to the primary triangular piece that catches the door frame, it has an extra component that prevents “shimming” the latch open with a credit card or pocket knife once it is closed. If door and frame alignment are incorrect or the lock is not installed properly, the lock does not have this added security feature. This is a common problem when locks are installed by anyone other than a professional locksmith. Security breaches or lock failures are a common result of improperly installed deadlatches. See also strike.