Abstract: A wrench selector provides for the quick and accurate checking of the dimension of a nut or bolt across the flats thereof, in order to determine the corresponding size of the wrench or socket required for use therewith. The selector incorporates two jaws, with the first jaw extending from an elongated scale and the opposite jaw extending from a body sleeve through which the scale slides. The scale includes several rows of dimensional numbers thereon, with each of the numbers corresponding to a distance between the two jaws. The numbers are staggered diagonally across the face of the scale, in order to spread them for greater legibility. The body or sleeve includes a set of windows spaced laterally thereacross, which in combination with the diagonal array of dimensional numbers, results in only a single one of the dimensional numbers being exactly aligned within a corresponding one of the windows for any measurement.