My friend bought these and I was skeptical and didn't buy them. I borrow one of hers and fell in love with it. She bought them at a show and got a good price. I'll be buying them at the next quilting show. I put my ruler with the markings up against the slide lock and it worked great. Now, I'm used to the fact there are no lines on the sidelock and feel comfortable with using the markings on my cutting mat. It did take some getting used to.