A crocodile clip (or spring clip) is a temporary electrical connector, named for its resemblance to a crocodile's jaws. Functioning much like a spring-loaded clothespin, the clip's two tapered, serrated jaws are forced together by a spring to make them grip a metal object. One of the jaws usually has either a wire permanently attached or a 4 mm banana plug inserted into it, for connection to an electrical circuit. The clip may be partly covered by a plastic shroud or "boot" to prevent accidental short-circuits.
Smaller versions are used in electrical laboratory work. These have a slightly different shape and are called alligator clips.
Large versions of these clips, called automotive clips, made of bare copper, are fitted to car jumper cables, which are used to transfer energy from a charged lead-acid battery to a discharged one.
Alligator clips are used in dental offices to attach a protective bib over the patient's clothing.
A Kelvin clip is a type of crocodile clip where the 2 jaws are insulated from each other. 2 wires connect to each clip. This enables 4 wire circuit measurement.