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 to the top of an anvil. A form of bench dog with either a curved or flat top, a traditional holdfast has its shank slid loosely into a dog hole until the tip of its hook touches the work, then set by striking its top with a mallet or hammer, which wedges the shaft tightly against the sides of the hole; a tap on the back near the top releases it again. Contemporary holdfasts are commonly sized for three-quarter-inch holes, somewhat narrower than the traditional standard, and scrap wood or leather is often placed between the holdfast and the workpiece to avoid marring it. A threaded adaptation, sometimes called a screwdown, is tightened into place rather than struck with a mallet.