There is a form of headless wire nail, known as a =barbed dowel-pin=, which is made as shown in Fig. 3 (_k_). This type of nail, or dowel, is used for doweling through the mortises and tenons of sash, blinds, and frames of every description. In the mill, it has displaced the wooden dowel used in former times. The length of pin to be employed is regulated by the thickness of the wood to be secured, as the pins are used ¼ inch shorter than the thickness of the woodwork. [Illustration: FIG. 4] An exceptionally heavy nail, or spike, is made from heavy wire or round bar. These spikes are used for heavy construction work, such as splined flooring, for slow-burning mill construction, and for bridge flooring. They are made with both chisel points, as shown in Fig. 4, and diamond points, and in ordering them, the kind of point, as well as the style of head wanted should be specified. Spikes of this kind are made in all sizes from tenpenny, which is of No. 6 gauge and 3 inches long, to spikes ⅜ inch in diameter and 12 inches long. =7. Galvanized Nails and Spikes.=—Nails and spikes, either cut or wire, that have been dipped into molten zinc and become coated with this metal are termed =galvanized=. By this process they are rendered practically rust-proof. Cut or wire galvanized nails can be obtained in the same sizes and types as ordinary nails, and if dealers do not regularly carry them in stock, they will as a rule have them galvanized to order. In order to secure durability, it is advisable to use galvanized nails in places that are exposed to dampness, as in shingling, in slating, in fence building, or in structures erected near the seashore, as it has been proved by numerous tests that ordinary nails rust through in such places in a few years. The galvanized nails cost from $1.50 to $3 more per keg than the plain cut or wire nails. The cheaper grades of galvanized nails are frequently coated only with lead, and will not withstand the government test; that is, dipping them into vitriol. A simple way to test the coating of a galvanized nail is to rub the nail on a piece of white paper. A lead-coated nail will mark the paper the same as a lead pencil and should be rejected, as it is only a sham and has no redeeming qualities. WOOD SCREWS, EXPANSION AND SPECIAL BOLTS =8. Wood Screws.=—The ordinary =wood screw=, which is one of the staple articles of hardware, is very necessary in the application of all builders’ hardware about the building. Except in some lines of cheap or rough, unfinished goods, hardware manufacturers now pack with all hardware, screws that match the finish of the goods. The various types of screws now on the market are illustrated in Fig. 5, and the common types, such as flat-, round-, oval-, and fillister-headed screws are easily procured.