An air ratchet is a power tool that uses compressed air to turn a ratchet drive. The air ratchet is used to speed up removal and initial bolting down of smaller nuts and bolts. A manual torque wrench is normally used to do the initial loosening and final tightening. The air ratchet is used to finish the process, in much less time than it would take by hand. For some jobs, such as working on engines, an air rachet should only be used for disassembly. Used for engine assembly it can easily result in stripped threads and broken bolts. Air ratchets consume a lot of air, so a large air capacity air tank and compressor are desirable.