This is a great tool for marking reference lines to use when creating circular designs where you want even repeats. Use it to center designs in blocks. The Westalee Desgin 6 Point Cross Hair Ruler is for marking 3 (120degree), 6 (60degree), 12 (30degree), or 24 (15degree) reference lines. Great for hexagon quilt patterns! The 12-1/2in size allows you to mark up to 12in blocks.