Dancing rulers!
Finally, I solved the dilemma of my long ruler dancing across my fabric while trying to cut long strips. I had purchased and was using the Invisigrip by Omnigrid...not impressed. Years ago my father-in-law gave me some sandpaper that is sticky on the back. Works like a dream. The only problem is that you can't see thru it, so I just cut it into small squares and place it randomly on the ruler. I don't know what it cost, but it is probably cheaper than the Invisigrip I had purchased.
The only problem I am having now is that it grips too good...no more sliding the ruler around on the fabric. I have to pick it up and place it where I want it, but guess what? I have true straight cuts.