The most common use of Cage Nuts (captive panel nuts) is to mount lighting systems, electrical equipment, or other instrumentation onto rail racks. They are often seen used on computer server racks. The Cage Nut clips into the rack's square mounting hole and usually positions the nut toward the inside of the rack.

Cage nuts provide several benefits over threaded holes. If a screw is over-tightened, the nut can be replaced, unlike a pre-threaded hole, where a hole with stripped threads becomes unusable. Cage nuts are easy to use on materials too thin or soft to be threaded. The nut is usually slightly loose in the cage to allow for minor adjustments in alignment. This reduces the likelihood that the threads will be stripped during equipment installation and removal making it easy to install/remove parts repeatedly without causing stripping expensive components.

Cage nuts are primarily available in steel, though some sizes are available in stainless steel via special order.