So I am squaring up my pinwheels with a 12 1/2" square ruler and it keeps slipping on me. Tried that Ruler Grip; won't stick to an Olfa mat. So I remembered I had gotten some little clear anti skid pot pads in the hardware aisle of Wal Mart. There are several sizes in the pack. I put 2 on each side so they don't interfere with my pinwheel seams. Give just enough height to keep the ruler from pivoting on the bulk of the center seam. And VOILA it worked! No more skidding. I am going to get a mess more of these things to put on all my rulers. I threw the package away so I can't tell you the name. But they work GREAT!