These are made in many sizes and degrees of stoutness, and of both brass and iron. In Fig. 448, a is the ordinary "gimlet pointed" wood screw; b is the Nettlefold, with a stronger kind of thread ; c, a stove screw; d, head of brass lock screw; e, head of japanned lock screw, f is a screw box for cutting wooden screws, costing 5s.-15s. Screws are made of the following lengths: 1/2, 5/8, 3/4, 7/8, 1, 1 1/4, 1 1/2, 1 3/4, 2, 2 1/4, 2 1/2, 3,3 1/2, 4, 5, and 6 in.; and in each length there are 12-30 different thicknesses, called "numbers."