alligator clip, bulldog clip - a clip with a spring that closes the metal jaws

chuck - a holding device consisting of adjustable jaws that center a workpiece in a lathe or center a tool in a drill

holding device - a device for holding something

pair of pliers, pliers, plyers - a gripping hand tool with two hinged arms and (usually) serrated jaws

bench vise, vise - a holding device attached to a workbench; has two jaws to hold workpiece firmly in place

spanner, wrench - a hand tool that is used to hold or twist a nut or bolt