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 in 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.

History

Based on a fresco discovered in the ruins of Herculaneum, holdfasts are known to have been in use since at least the 1st century AD. They are also described and illustrated in early European books on woodworking, such as Joseph Moxon's 1678 edition of Mechanick Exercises and André Jacob Roubo's 1774 ''L'Art du Menuisier. '' The term has been in use since at least the 16th Century. Use declined throughout the 20th century, but has seen a resurgence in recent years. While "artisan" holdfasts continue to be made as castings, or forgings, modern holdfasts are made from round mild steel bar stock using highly automated cold-working machines. Gramercy Tools makes such holdfasts from bar stock which is slightly under 3/4" (19.05mm) dia., usually 19mm for use in the now customary 3/4" bench holdfast holes. The making of such a holdfast is more particularly described in Gramercy Tools' patent document (U.S. Patent 7,571,631, to Moskowitz, et. al.).

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