Friction Hitches for Climbing 

the limiting factor of any cord or line to create a hitch is the lines ability to create the smallest circle when you "pinch" a tight bight and the tension of the cord internal diameter (compression) and the outer diameter (elongation) reach a point where they cannot be made smaller. often called the pinch test. a good reason to use sewn webbing runners as hitches, more surface area and the "pinch" is practically zero in diameter.