Piggyback terminal connectors are often used in a variety of kiln manufacturers' control boxes. When crimped onto the end of a wire it allows a second tab connector to be connected to the same tab. Sometimes called blade or spade connectors.
You might find these used to jump off to a pilot light or for jumping to another relay or switch.
Cone Art Kilns use these as well as some older L&L Jupiter Kilns.
16 - 14 AWG