Once a common snapped lock has been installed on a system door, its presence should be evident. A common snapped lock is very similar to a double cylinder deadbolt. The only difference between the two being that the locking mechanism of a common snapped lock will punch out in order to allow for a key to be inserted from the outside of a door and turned. This means that once access has been gained through any means, inserting and turning a key in the door's latch allowing it to fully open is as simple as inserting and turning said key... read full review »