From what I can gather, the locking switch would not replace keyswitches that, when pressed, activate a "lock" function, such as Caps Lock, Scroll Lock, or Num Lock. The lock switch would rather replace a normal momentary closed switch, in order to keep the switch closed after it is pressed, and activate that keypress until it is pressed again to open the switch. For instance, if you replaced your left shift keyswitch with a lock switch, once you activate the left "shift lock," YOU WOULD GET CHARACTERS LIKE THIS INCLUDING THE NUMBER ROW< ETC>< !@#$%^&*()_+> WHEN YOU PRESS THE LEFT SHIFT AGAIN TO DEACTIVATE IT< you would cancel the lock. You could theoretically replace any modifier switch with a lock switch, but I don't know how often you would need to keep a modifier, e.g. Ctrl, Alt, Win, Menu, held down like that. Maybe like dorkvader said, for a Fn-lock.
