Holdfast (tool)

A holdfast or hold fast is a form of temporary clamp used to hold a workpiece firmly to the top or side of a wooden workbench or the top of an anvil.

A form of bench dog, a traditional holdfast has either a curved or flat top. Its shank is slid loosely into a “dog” hole in the bench or anvil until the tip of its hook touches the work. It is set by hitting its top with a mallet or hammer, which causes the shaft to wedge tightly against the sides of the hole. A tap of its back side near the top releases it.

Contemporary holdfasts are commonly designed to fit in 3⁄4 inch (19 mm) holes, somewhat narrower than had been traditional. Scrap pieces of wood or leather are often used between the holdfast and the workpiece to prevent marring it.

An adaptation of the holdfast is threaded, sometimes known as a “screwdown”, which is tightened rather than tapped in place.