I love my Omnigrid 18" ruler with the little thing at the top that just rests on the edge of a mat. It holds fantastically and I just told my friend when we go out for a quilting binge that I am going to buy another one, just in case they are discontinued (and you know they will discontinue an 18" Omnigrid before they will discontinue an 8" Phillips screwdriver)!!!
Edie