Is your ruler slipping? If so, you need to apply something to it. There are several things, such as sandpaper dots, clear dots specifically for preventing slipping, Omnigrid Invisigrip (clear film), and even clear nail polish, but I haven't tried that one myself. Personally I like the Omnigrid Invisigrip. I have many rulers and used it on nearly all of them from just one roll. I even cut thin strips and put it on the back of my June Tailor Shape Cut ruler.