wire nut

[STEVETERRY]

A Listed device for splicing two or more conductors by winding them into a screw-pressure configuration. Wire nuts are rated by conductor gauge and number of allowable conductors, either solid or stranded. It is important to read the ratings of a given wire nut to make sure they match the splice application you are contemplating.


http://www.cableorganizer.com/thomas...connectors.htm

Usually plastic, although available in ceramic for high temperature applications.

A couple of specialized tools to ease the tedium of having to manually twist:


http://www.idealindustries.com/prodD...ing-nut_socket


http://www.licensedelectrician.com/S...ut_Spinner.htm