I have a hand held snap-q. I made sleeves to slide on one or two sides for when I have to quilt the edges or corners of the quilt. I safety pin the edge of the quilt to these sleeves to keep the tension. But my snaps don't have any ridges on the inside, they are completely smooth. Ladies used to pin the edges of the quilt to the big old quilt frames in basically the same manner. The one old 1 that I saw the ladies put batting on the rails and covered it with fabric to pin to.