A workpiece positioning apparatus comprises two sets of jaws mounted on a rigid elongate bar, the jaws being adjustable to provide repeatable spacing of any arbitrary distance between the jaw sets. When two pieces of lumber, such as wall studs, are inserted into the two jaw sets, they are positioned at the specified spacing along a stringer such as a wall bottom plate. Indicia are provided on the strip indicating the English or metric measure of the distance between corresponding parts of the jaw sets, as well as enhanced indication of typical, e.g., 16-inch and 24-inch centerings used in American homebuilding. 151/4 and 231/4 inch indicia are also provided for shorter spans needed at stringer ends and corners to accommodate 4-foot-wide panels. The gap between jaws on one or both of the jaw sets is further adjustable to fit the thicknesses of the lumber being used. Longer jaws can be used to assure perpendicularity of wider workpieces to the elongate edges of the supporting construction members.