Crocodile clip
A crocodile clip (also alligator clip) is a sprung metal clip with long, serrated jaws which is used for creating a temporary electrical connection. This simple mechanical device gets its name from the resemblance of its jaws to those of an alligator or crocodile. It is used to connect an electrical cable to a battery or some other component. 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 ~ 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 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, and are used with thick insulated copper cables to make connections between  automobile batteries. These jumper cables (a.k.a. 'jump leads') 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. The United States Defense Logistics Agency specifies several types of electrical clips in Commercial Item Description (CID) A-A-59466. In this CID document, crocodile clips are designated type CC, alligator clips are designated types TCx, and other types of electrical clips have various other, unique designations. Kelvin clip. A Kelvin clip is a special form of crocodile clip. The jaws  of a Kelvin clip are insulated from each other, allowing two isolated wires to connect to a single test point. This enables 4-wire measurement of circuits with very low resistances.