Found this on the website for International Association for Professional Quilters:
Do you want to keep your rotary blade sharp? Try The Cutting Edge ruler system from Sullivans and Pat Sloan. The ruler features full see-through, non-skid frosting and a unique red grid system that highlights the 1/2 inch marking. What is most unique about the ruler is it has an inlaid diamond powder edge that continually sharpens the blade that runs against its edge.