You tape a bit of the shelf paper on the back of the ruler and it won't budge when you are holding it down to cut. Put bigger pieces on the bigger rulers. It is that rubbery type shelf paper that we are talking about.
I use the non-skid shelving (kind of rubbery). I have a couple of strips cut and just place it under the ruler where I can hold the ruler still. When you move he ruler you move the strip. Just cut to a comfortable size.