The Killer Key can instantly and permanently disable a lock. Once inserted into a lock it can not be removed, making it impossible to unlock the door. (The door can still be opened from the inside, so no one can be locked in, only locked out.) The only way in is to drill the lock. Simple to deploy-just the keyway and then push sideways on the bow which will easily break off. The Killer Key can be a valuable tool for law enforcement as an instantly deployable access denial device. It feet s also a useful tool for property management to prevent return of evicted tenants before the locks can be changed. About 90% of the locks used in the USA use one of two key styles-Schlage or Kwikset, so a Killer Key version is available for each.