Crocodile clips

A crocodile clip (also alligator clip or spring clip) is a simple mechanical device for creating a temporary electrical connection, and is named for its resemblance to an alligator's or crocodile's jaws. Functioning much like a spring-loaded clothespin, the clip's tapered, serrated jaws are forced together by a spring to grip an object. When manufactured for electronics testing and evaluation, one jaw of the clip is typically permanently crimped or soldered to a wire, or is bent to form the inner tubular contact of a ~4 mm female banana jack, enabling quick non-permanent connection between a circuit under test and laboratory equipment or to another electrical circuit. The clip is typically covered by a plastic shroud or "boot" to prevent accidental short-circuits.

Small versions, ranging in size from 15–40 mm in length, are used in electrical laboratory work.

Large versions of these clips, called automotive clips or battery clamps, are made of solid copper for low electrical resistance, are used with thick insulated copper cables to make connections between automobile batteries. These jumper cables are capable of delivering hundreds of Amperes of current needed to directly power an automobile starter motor, or to transfer energy from a charged lead-acid battery to a discharged one.

Specifications
In the United States, the Defense Logistics Agency maintains Commercial Item Description (CID) A-A-59466 for several types of crocodile clips. This CID supersedes Federal Specification, W-C-440, which was cancelled in 1998.