Book 2 — Light in a Keyhole

Remove the lock and cut the mortise deep enough to admit a 3-volt battery lamp with a suitable socket attached. The lamp is then connected to wires which are concealed and run to a battery of three dry cells in the basement or other convenient place. A small push button is attached in the line and placed near the knob on the door. A small recess must be cut in the mortise so that the light from the lamp will shine directly on the inside of the plate over the keyhole.—Contributed by Armand F. Lamarre, St. Remi, Can.