I bought a Quilter's Guide Lock and when I got it, I thought it was a waste of money. I watched the YouTube about your gadget just now and now I understand. My Guide Lock is like your gadget. I didn't realize I was suppose to put a ruler under it. I thought it was suppose to come with ruler lines on it. It has been sitting under my sewing table for months. I just got it out and tried it with a ruler and it works great. This didn't cost very much money...less than $40, but I think it works the same way.