After trying all sorts of ineffective products to keep rotary cutting rulers from slipping, I've found a do-it-yourself solution that really works! I use clear silicone caulk. The kind you use for bathtubs. It comes in a tube, can be found at any hardware store, and costs 2 or 3 dollars. Squeeze a generous amount on your ruler and spread it thin, with an old credit card, to cover the whole back of your ruler. Let cure overnight, then scrape any excess from the edges. I've used it on several different brands of rulers and it hasn't damaged the marks and can be removed by scraping with your fingernail. The downside -- it smells bad until it cures, so apply it in a well ventilated area.
