And Ratchet because it has the same action but doesn't click.
P. Bodge is right, it's for gripping studs to get them out, the serrated grip is there all right but it's at the bottom. Very handy when you need it, much quicker than using two nuts and of course it works just as well on a damaged stud as long as there is enough for the grip to get hold of. Now this one is really easy....
