A scratching technique used to satisfy an itch on a scrotum. Nuts, unlike elbows, are carried by something called the nut sack. The nut sack is not a smooth surfaced piece of skin like the back or leg. It is actually skin with high elasticity which is often times folded back on itself and sort of scrunched up, especially while wearing clothes and sitting. A roller is performed with one hand, even with pants on, using thumb and forefinger, griping the nut sack in the general area of the itch, and rolling the pinched area back and forth until the itch is gone. The technique is not exactly a superbly accurate surgical operation but it gets the job done. Crude, maybe, but effective.
(Thinking to myself at work) "I really need to scratch my nuts but I don't want anyone to see me reach into my pants. I'd better use the roller under my desk."