[abisel]

The Impact driver is totally mechanical. Select the tip, select direction of rotation, place tip into screw, hold the driver securely with a slight force into the screw, and hit the end with a hammer. Not some light-weight trim hammer either, but a large ball peen or drill hammer.

Tip: to determine if you have the correct rotation selected, put the tip on a flat surface and push down on the driver and observe direction of tip rotation. Remember, righty-tighty, lefty-loosly.