[JhwShark]

Originally Posted by Danglerb

Impact driver is a metal cylinder about 1" x 6" usually with a male 3/8 square drive on one end and flat on the other for smacking with a hammer. They have an adapter and half a dozen large blade and Phillips style bits, so you will need a set of hex bit 3/8 drive impact sockets to go with one.

With a tough bolt I "lightly" seat the bit socket first into the bolt head with a hammer, then put the impact driver on the bit socket taking care not to loosen it, then give it a smack with the hammer. The smack slightly collapses the impact driver and causes it to rotate the bit socket at the same time. First time you use one you will know you have met a friend for life.

Nice description!

If you need to buy the sockets they need to be impact sockets or you could crack the socket.