Locking clamps either refers to a C-shaped jaw clamp or a Sheet Metal Butt Welding Clamps

A C-shaped jaw clamps are controlled by a screw and lever mechanism and have one fixed jaw and one moveable jaw this is controlled with an integrated lever which when pressed rapidly closes the moveable jaw, the screw is used to tighten the jaws to adjust the pressure applied on the workpiece. Some models have a wide jaw opening enabling them to grip workpieces of various shapes and sizes including tapered and irregularly-shaped objects as well as extremely thin materials i.e. sheet metal.

A Sheet Metal Butt Welding Clamp holds sheet metal edge to edge at the correct gap to produce clean welds reducing grinding after completion. They can hold flat, curved and pressed ribbed panels, they are helpful for assembling, fabricating patch repairs and reskinning. They are used by loosening the wing nut to allow space for the metal sheets to be placed between the base of the clamp and the toggle bar, the wing nut is then tightened to lock the sheets together ready to be tack welded after which the clamp can be removed before the final weld is done.