This is one of the oldest binding methods. I believe that the more common sewing on tapes is a later development. Sewing on cords is not qute the same in that the thread passes round the cord and returns back into the folio via the same hole as it left. When sewing ~ in a frame ~ on tapes it is possible to tap down the sections fromtime to time and evenout the spacing along the hinge. When sewing on cords this gentle slippage up and down the cord is rarely possible. the secftions have to be accurately placed adjacent to each other right from the start.