Cage Nut

A cage nut is a type of fastener consisting of a square nut encased in a spring steel cage. The cage has wings that compress to allow it to be inserted into a square hole on a panel or rack. Once inserted, the wings expand, securing the nut in place and allowing a bolt to be screwed in. They are commonly used in server racks and other applications where a threaded hole is needed in a thin sheet metal panel.