a well-known tool used by mechanics, consisting of an iron head fixed crosswise upon a handle of wood. There are several sorts of hammers used by blacksmiths; as, first, the hand-hammer, which is of such weight that it may be wielded or governed with one hand at the anvil; second, the up-hand sledge, used with both hands, and seldom lifted above the head; third, the about-sledge, which is the biggest hammer of all, and held by both hands at the farthest end of the handle, and being swung at arms' length over the head, is made to fall upon the work with as heavy a blow as possible. There is also another hammer used by smiths, called a riveting hammer, which is the smallest of all, and is seldom used at the forge unless upon small work. Carpenters and joiners have likewise hammers accommodated to their several purposes.