Abstract: There is disclosed herein an improved apparatus for use in accurately determining the proper position for the line of demarcation between the bifocal correction lens and other corrective lens segments to be provided in eyeglass lenses. The measuring apparatus includes an elongated indicia carrying member having provided thereon adjustable clamping members specifically designed to enable the elongated member to be attached to a wide variety of eyeglass frames for purposes of obtaining a measurement of the proper height for location of the segment line. The elongated member also includes a sliding gauge which may be moved therealong and cooperates with the indicia to provide an accurate, easily determined measurement for the position of the segment line.