"With the Corbin Unit Lock, there is no groping in the dark--no guessing at the probable distance of the keyhole from the knob. As you grasp the knob, the keyhole comes to meet you..." The Corbin unit lock with the keyhole in the knob is good hardware. P. & F. Corbin, since 1849. The American Hardware Corporation, successor. 1922. Click here to enlarge.