This is a great way to easily and accurately burnish your card scrapers quickly. Clamp your scraper, set your preferred hook angle, and roll that edge giving you a perfect card scraper hook every time.
There's a tungsten carbide rod held at exactly the right angle as you burnish. The injection-molded body keeps hands clear of sharp edges. It also makes it easy to apply as much pressure as you need. Nylon body with brass fittings.