Sharpen your rotary cutter blade with every cut!The Cutting Edge Quilting Rulers from Sullivans feature a patented design with a diamond carbide edge that sharpens rotary blades with every cut! These revolutionary rulers are marked with easy-to-read numbers, square-up guides, and diagonal dots that make lining up cuts quick and accurate. The fully frosted backing gives you the right amount of steadiness for cutting, but also allows you to slide the rulers when needed. The unique red grid system is designed to highlight the 1/2” markings which are there for you to "tuck" your block into. Use the inside edge of the red angle to cut squares and trim up blocks.