When I first saw this tool I thought to myself, "why would I need this I can just free hand curves". Now that I own it I have completely changed my mind. The ruler helps you visualize what the curves will look like on the paper prior to making any cuts. This really help me from drawing a curve and errasing it because I don't like it or wasting paper because I don't like it once it is cut out. For us visual people, you can keep moving the ruler around until the curves look just right, them mark and cut. I sometimes like to cut the paper into a curved strips. Because the sides of the ruler are rigid you can make a pencil line on both side of the ruler giving you two lines to cut out the curved strip of paper.