A positioning device for a power tool. A tool, such as a drywall screw gun, is equipped with a projector which projects two light rays, which form a "V." The axis of a screw driven by the gun lies in the plane of the "V," as by bisecting the "V." If the two rays are positioned so that they illuminate a framing member, such as a 2.times.4 stud, then this axis will intersect that stud. In effect, (1) the stud becomes the horizontal base of a triangle, (2) the legs of the "V" become the sides, and (3) the axis becomes the altitude. The altitude (axis) necessarily intersects the base (stud). This intersection occurs whether or not a sheet of material, such as drywall, covers part of the stud, provided extremeties of the stud are exposed for the illumination described above. Thus, the location of the concealed part of the stud can be determined, despite the fact that a sheet of material obscures that part.