Thanks everyone

I do this too, only in thin strips down the ruler. I havent had a problem with slipping since. And I'm a heavy pusher.

I'm gonna try it.... :D

The height of your cutting table is important.
Im short so cutting tables are to high for me. I bought a small stepstool that puts me well above the table. Now I have more traction when cutting and no more problems.

Have you considered cutting your fabric in lengthwise strips (parallel to the selvage) instead of crosswise?

When I cut my strips lengthwise, I at least will have two edges on grain.

I also do better with only a couple of layers at a time. Might take me a bit longer to cut stuff, but if I do goof up, there is less fabric wasted.

The other suggestions to make your ruler more slip resistant are definitely worth following.

Bev ~ I used to have the same problem and I attributed it to the fact that I wasn't able to apply the right amount of pressue on my rulers. My hands are small and I think some arthritis these days.lol. So, I bought a "Gypsy Gripper" and it has made all the difference in the world. It is a handle with suction cups that are applied to the acrylic ruler. Nita

Bev-these are all great tips. I have this same issue and I discovered that part of my problem was the angle at which I was holding my rotary cutter. If I hold the cutter lower and more parallel to the cutting mat then I was more likely to "shove my ruler" to the side and get a crooked cut. I now hold my rotary cutter higher-more upright, then I get a straight cut. You are only pressing down over the blade and not pushing the blade along. It really helped me. I have arthritis really bad in my thumbs, so I cannot spend a long time cutting at any stretch-I like for every cut to count.

That's what the gal told me yesterday when I was at Walmart......

There's a new tool called the Gripper (I think). It's basically a handle with suction cups that stick to your ruler, so you can just press down on the handle and you don't have to do that spider think with your hand.