My husband made my PVC quilting frame.....used 1 in pipe. He ground the side off the 1 inch pipe to make the clamps. He said the grinding was a "great mess!!" but it works. He sanded the edges smooth and rounded the ends. This fits over over the quilt quite nicely. It does not have ridges, but I have had no problems with my quilt slipping when it is in the frame. I have extra clamps in various sizes.