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. This is important not only because it can be easily done by someone who has gotten past a door's lock, but also because of the security risk this presents. If an intruder were to break into a home and attempt to open all the doors in the house, they would likely come across a common snapped lock and not even realize it. As long as their key was valid for the locks, they could simply insert it turn and have access to that room. Once inside, they could do anything from stealing valuables from whatever room they were in or leaving through the front door if said pathway was left unguarded. That is why most snap locks require special attention when used on exterior doors of houses or apartments. Common snapped locks are often seen on business doors. So much so, that businesses like hospitals and schools often will have keys professionally cut for the lock in order to ensure that a copy of said key does not exist anywhere outside of the building. This is because if a burglar were to get into a hospital or school, all they would need is one key to be able to gain access to every room inside.