During World War II, many radio tubes were unavailable, and the magazines were full of ideas on how to cope. The April 1944 issue of Popular Mechanics showed how to make adapters to use similar tubes that might be available, but used different base types.

In particular, the magazine pointed out that loctal tubes were often available. Therefore, the adapter shown here allows a loctal tube to be plugged into a standard octal socket. The bottom half of the adapter was a defunct tube (probably the one being replaced), and the top half was a socket to match the new tube.