A Jack stud is a partial-length stud that serves as a stilt or brace underneath each end of a header. Installed in pairs and fastened to the king studs, these define the left and right inside dimensions of the rough opening. Also referred to as a trimmer stud

A jig saw is avariable speed handheld saw with a flat base is used to cut curves out of material using a small straight reciprocating blade

A junction box is a plastic or metal enclosure that houses outlets, switches, wire ends, and connections for user and fire safety purposes