Iron screws are made with either flat, round, or oval heads and the following finishes: Bright, blued, japanned, tinned, galvanized, bronze-plated, brass-plated, coppered, silvered, and nickel-plated. Brass and bronze metal screws can also be procured with flat, round, or oval heads, in either natural color or, on special order, finished to match the hardware. Special screws are also manufactured for various purposes, which are sufficiently explained by the illustration, Fig. 5. [Illustration: FIG. 5] Screws are always measured for length from the point to the top of the head. The sizes in which screws can be obtained are given in Table IV. The diameter of screws is always measured directly under the head, and is always given in numbers of the screw makers’ gauge. The numbers vary from 0 to 30, going consecutively without skip from 0 to 18 and from then on using only the even numbers. In Table IV are also given the numbers of the screw makers’ gauge and their equivalents in decimals of an inch. TABLE IV SIZE OF WOOD SCREWS =======+========================= Length | Diameter in Inches | Screw Makers’ Gauge -------+------------------------- ¼ | From 0 to 4 inclusive ⅜ | From 0 to 9 inclusive ½ | From 1 to 12 inclusive ⅝ | From 1 to 14 inclusive ¾ | From 2 to 16 inclusive ⅞ | From 2 to 16 inclusive 1 | From 3 to 20 inclusive 1¼ | From 3 to 24 inclusive 1½ | From 3 to 24 inclusive 1¾ | From 5 to 24 inclusive 2 | From 5 to 24 inclusive 2¼ | From 5 to 24 inclusive 2½ | From 5 to 24 inclusive 2¾ | From 6 to 24 inclusive 3 | From 6 to 26 inclusive 3½ | From 8 to 26 inclusive 4 | From 8 to 30 inclusive 4½ | From 12 to 30 inclusive 5 | From 12 to 30 inclusive 6 | From 12 to 30 inclusive ------+------------------------- SCREW MAKERS’ GAUGE --------+--------------- Number | Equivalent of Screw| in Decimals Gauge | of an Inch --------+--------------- 0 | .05784 1 | .07100 2 | .08416 3 | .09732 4 | .11048 5 | .12364 6 | .13680 7 | .14996 8 | .16312 9 | .17628 10 | .18944 11 | .20260 12 | .21576 13 | .22892 14 | .24208 15 | .25524 16 | .26840 17 | .28156 18 | .29472 20 | .32104 22 | .34736 24 | .37368 26 | .40000 28 | .42632 30 | .45264 ========+===============