How to tie A Double Fisherman’s Knot
The Double Fisherman’s Knot (also known as; Grapevine Knot or Grinner Knot) is used to join two lines of rope or fishing line together. This knot is very strong and reasonably secure, but it does have a high tendency to fail with larger Dyneema/Spectra’s cords when put under heavy loads. The outer sheath first fails, and then the cord slips thought the knot. This is why, when climbers use this knot they tend to opt out of the Double fisherman’s knot, and go with the Triple Fisherman’s Knot, where this flaw doesn’t happen.