Every machinist knows then pain. You've nearly finished a part, you place it in your vide to deburr it, and turn the handle a little to aggressively, leaving the pattern of the knurled jaws stamped into your work.
The magnetic soft jaws are placed within the jaws of a standard vise, protecting th ework and providing a soft, grippy surface. I manually cut the knurling on my restored Burke Millrite.