the cording (rope) is approx. 3 inch in diameter encased in a pocket the remainder for attaching the quilt top is about 6 1/2 inches it is 120 inches long with hems and seams I suspect initially the piece was 10-11 inches width (thee goal is after putting the cording in is to have that six inches to quilt the top of the quilt so you don't need more fabric than required for backing. Hope this helps.
FYI Also there is you tube video on attaching the fabric. Also Brother dream frame uses same concept also a video on loading .