This function describes locks that can be left locked or unlocked with only a key. These are ideal for the front door of a retail space or group home because the manager can leave the door unlocked for business but nobody can come along and lock the door by pushing a button or toggle switch. This gives the manager of the space ultimate control of whether the door is locked or unlocked. It is always unlocked from the inside.
The classroom lock unfortunately can be accidentally left unlocked. To lock this lock one must usually rotate the key 360 degrees when leaving. This isn’t very complicated, but it is more complicated than a deadbolt which has an audible and visual confirmation that the door is locked.
These locks retail for $233 from the Schlage L series.