I use the Gypsy Gripper Little Gripper that fits on small rulers. It is 2 1/4 " round. I don't use a rotary cutter without a safety tool and this works great to hold the ruler flat and to protect my fingers. Grippy spray does a great job for smooth bottom rulers. With Quilter's Select rulers, which are my favorite, I use a ruler handle because they will not slide and the handle makes it easy to move the ruler on the fabric and of course protection.