I bought the Sullivans The Cutting Edge 6 1/2" square ruler because it was on sale and I wanted to try it. The ruler is fine and I like the red line markings on it but I'm not sure that the metal edge really sharpens my ruler. I can hear the rotary blade scraping against the metal strip but I really haven't noticed that my blade is a lot sharper. If you needed a new ruler, it works but I don't think I'd buy it with the goal of sharpening my blade.