Heavy-duty extruded aluminum lock with steel thumbscrew for use on metal horizontal sliding windows. For a non-heavy-duty lock see item no. U-9980 or U-9982. Finish by tightening thumbscrew with pliers to securely lock windows in closed or ventilating positions. For a non-marring lock see U-9820, U-9821, U-10876 and U-10551. For vinyl windows use U-9809 or U-10547.