HAMMER, an implement consisting of a shaft or handle with head fixed transversely to it. The head, usually of metal, has one flat face, the other may be shaped to serve various purposes, e.g., with a claw, a pick, etc. The implement is used for breaking, beating, driving nails, rivets, etc., and the word is applied to heavy mases of metal moved by ma chinery, and used for similar pur poses. (See TooL.) The word is also applied to many objects resembling a hammer in shape or function. Thus the "striker" in a clock, or in a bell, when it is sounded by an independent lever and not by the swinging of the "tongue" is called a "hammer"; similarly, in the "action" of a pianoforte the word is used of a wooden shank with felt-covered head attached to a key, the strik ing of which throws the "hammer" against the strings. In the mechanism of a fire-arm the "hammer" is that part which by its impact on the cap or primer explodes the charge. (See GUN.) The hammer, more usually known by its French name of snartel de fer, was a mediaeval hand-weapon. With a long shaft it was used by infantry, especially when acting against mounted troops. With a short handle and usually made altogether of metal, it was also used by horse-soldiers.