I just bought the coolest thing for putting on your ruler so you can hold it in place while you cut and keep your fingers off the edge of your ruler. I teach sewing and teach my kids how to use rotary cutters but I'm always freaked out when they use them, afraid someone might cut their finger. These come in 3 sizes, the largest one I felt was just too big, the medium one seemed just right, and I bought a small one too just because.
I got mine from Pine Needle, their website is www.pineneedlequiltshop.com. They are in Lake Oswego, Oregon.