The script attached to this event fires when when an object has been locked.
The door or placeable object has been locked by another object.
GetLockLockDC() returns the DC to use the Open Lock skill to open the lock.
Only placeables that can be opened can be locked or unlocked.
OnLock and OnUnLock didn't use to work. As of patch version 1.29 (or probably 1.28), the events fire as they should.