I draw mandalas on small 3.5 inch plaster stones that I cast myself. Finding the center is a basic requirement for a mandala. If you get it wrong by even a fraction, it will ruin your entire design. Finding a center on these stones was particularly difficult as they slope down the entire edge. This tool is a lifesaver for me! Just put a round stone, mark 3 lines and the intersection of these lines is a dead point. I also used it on a square canvas - again perfect. This tool works on small objects, so now I need to find one that works on a 12 inch canvas. Overall, I love this tool and would happily pay twice as much!