I use sticky back sand paper pieces. I put one in each corner and then a couple around the ruler. For a 6" x 18" ruler, I probably use about 12 small pieces of sand paper. Grips fabric really, really well. I have also thought of using the " gel dots" they sell in the scrapbooking section of Walmart/JoAnn, but not too sure how these would work.
Great idea, Misseva! We quilters sure are an inventive bunch!
Anita