The secret to the compact functionality of the Woodpeckers Box Clamp is it's tapered wedge design, (only one moving part), that simultaneously pushes the mating materials down and in with less then two turns of the screw while applying an enormous amount of clamping force. Just one Box Clamp can save you time and aggravation as it instantly squares up your box sides and holds them in place for gluing, screwing or nailing. Accomodates assembly of 2 different panel thickneses (up to 1/4 difference). Molded from glass reinforced polycarbonate. Includes hardware for use as part of a clamping fixture or un-fixtured for large cumbersome projects. Each Woodpecker 4” Box Clamp is made in the U.S.A.