These wrenches are used in a similar manner to a ratchet. The wrench will grab the flat on the hex in one direction only. In the reverse direction the wrench will slip to the next flat. This feature allows the user to leave the wrench on the hex and rotate the hex without the need to remove the wrench to grab the next flat.
About 10 years ago Craftsman came out with these style wrenches and marketed the crap out of them at Christmas. My brother got a small set from his wife who didn't know any better, we hated them. Worthless except in certain situations. Another gimmick by Craftsman I thought. I own quite a few Snap On tools, didn't even know they made them.