How to tie a double fisherman knot to rig a ring of corde for belay on natural anchorage - Application: Used to create a joining loop from two ropes or a cord, a knot that allows connecting two ropes of different diameters for rappelling. Ideal for creating a permanent loop on a natural anchor. - Advantages: Excellent holding strength. - Disadvantages: Very difficult to untie, bulky, risk of getting stuck when pulling the rope. - Breaking strength: 19 kN - The tail strands must have 8 to 10 cm of free length