Impact wrenches, power torque wrenches, and power ratchets have a square drive for holding interchangeable sockets that are used to turn nuts and bolts. Impact wrenches use impact-rated sockets and combine a hammer-like impact with high rotational torque to drive and remove large or frozen fasteners. Power torque wrenches use gear reduction rather than an impact mechanism to apply a predetermined amount of torque to fasteners in applications where overtightening can damage parts. Power ratchets have compact heads for working in tight spaces and allow precise control of positioning and rotational torque for applications where high torque isn't required.