This section is from the book "The Boy Mechanic Vol. 2 1000 Things for Boys to Do", by Popular Mechanics Co.. Also available from Amazon: The Boy Mechanic, Vol2: 1000 Things for Boys to Do.
In making small switchboards, rheostats, and other electrical devices, I found a good use for old center-fire cartridge shells as shown in the sketch. A hole a little smaller than the diameter of the shell is made in the board and the shell is forced in. The proper wires are then soldered to the metal on the inside, or the Wire may be placed inside of the shell and held in contact by driving a wood plug in as indicated. - Contributed by W. O. Nettleton, Washington, D. C.
Ill: The Heads of the Cartridge Shells Make Good Contacts for a Switch Lever