The Lock Industry Standards and Training Council defines function as “a set of operating features for a particular type of lock or exit device which make it suitable for a specific application." Lock function is identified mainly by the method of retracting the lock. Depending on the type of lock, any of the two standards, ANSI/BHMA A156.2 standard for bored and pre-assembled locks and latches or ANSI/BHMA A156.13 standard for mortise locks and latches, may be adopted. Following is a list of common functions for mortise locks.
The lever or knob on either side can be used to retract the latch. This is a non-locking function.
The latchbolt can be opened using the lever or knob from either side. From inside, the turnpiece can be used to make a deadbolt. Similarly, from outside, a key can be used to make a deadbolt. The inside lever or knob can be used to retract both the deadbolt and latchbolt.
The outside lever or knob can be locked using a toggle attachment. If it is not locked, the latch can be retracted by turning the lever or knob on either side.
The outside lever or knob can be locked from outside using a key. If it is not locked, the latch can be retracted using the lever or knob from either side. The key lock and unlock function is for the outside lever or knob only. The inside lever or knob is always active. There is no deadlock.
The latch of this type of lock can be retracted by using a key from outside or using the lever or knob from inside. The outside lever or knob is not active. A key is required to open the lock from outside. There is no deadlock.
ANSI-F09 (Public entrance)
Outside lever can be locked by key from inside. If it is not locked, the latch can be retracted by the lever from either side. There is no deadbolt. Using a key outside, the latch can be retracted.
Either of the levers can be used to retract the latchbolt. The deadbolt cannot be retracted using the inside lever. The key can be used on either side to open the deadbolt.