The two principal classes of braces are named crank braces and swing braces. A crank brace is used to rotate broaches and to drill small holes with drills; a brace of this sort is shown by Fig. 360. When a hole is to be drilled in a corner, there is not sufficient room for a cranked brace to revolve, therefore a swing brace is used; one of these is indicated by Fig. 363, which swings to and fro only a third, or sometimes only a quarter, of a revolution of the handle. Swing braces are named also ratchet braces, because they are worked my means of toothed wheels, named ratchets. While a ratchet brace is in use, the lever, or handle, is pulled forwards and backwards, instead of being entirely revolved in the manner of a cranked brace. To make this alternate motion capable of rotating that portion of the brace which holds the drill, a pawl is fixed to the lever so that one end of the pawl shall be held in a gap between two ratchet-teeth while the drill is rotated forwards for cutting, and shall slip over the tops of the ratchet-teeth while the handle is moved backwards during the time the drill is not cutting. By this means the lever is pushed backwards without moving the drill; this remains stationary until the pawl is again engaged with the ratchet to advance the drill another portion of a revolution. This gradual process of making holes is well adapted to large holes that cannot be made with a cranked brace, which has but little power when compared with the long handle of a swing brace; but little power can be exerted with a cranked brace, through the shortness of its levers, but a swing brace may have a handle of any length which is not too long for the strength of the instrument; such tools being made of all sizes, and capable of making holes from an eighth of an inch in diameter to three inches.