Workshop tools are divided into two classes, hand-tools and machine tools. The former class includes hammers, chisels, files, ratchet braces, spanners, etc. The latter class includes lathes, planing, shaping,drilling, and slotting machines, used in the fitting shop; and punching and shearing machines, bending rolls, and steam hammers, used in the smith's shop. The compressed air attachment (Fig. 8) is a good example of a power tool.