Double Fisherman's Knot
Also known as: Grapevine Knot
bend knot
Life-safety notice
TyingPoint's illustrations are for learning. For any life-safety use — climbing, rope access, rescue, or load-bearing rigging — seek qualified in-person instruction, and always inspect and test every knot before you trust your weight (or anyone else's) to it.
There is no bend climbers trust more to hold a closed loop of cord together than the double fisherman's, and the reason comes down to what happens under load rather than how it looks tied. Two double overhand knots, each tied around the opposite rope, slide toward each other and jam hard the instant the two standing parts are pulled apart - the harder the pull, the tighter the jam, which is precisely the behaviour wanted for something like a prusik loop or a joined rappel rope where slipping simply isn't an acceptable failure mode.
That same jamming is the knot's well-known drawback. After a genuinely hard load - a fall onto a prusik loop, for instance - the two knots can lock together so tightly that untying them by hand becomes a real struggle, sometimes needing a marlinspike or similar tool to work the strands loose. Climbers who expect to untie a rappel-rope join repeatedly through a day of raps have increasingly turned to the zeppelin bend instead for exactly this reason, even though the double fisherman's remains more universally trusted for a permanent closed loop.
It is also the traditional knot to close a length of cord into the loop used for a prusik hitch, and it remains standard equipment knowledge for anyone building an improvised rescue or hauling system.
Search-and-rescue technicians favor the same jamming behaviour for a related reason: a knot that's genuinely difficult to work loose under load is exactly what's wanted when joining two rope ends that must never separate mid-rescue, even at the cost of extra effort untying it afterward during equipment breakdown. Some climbers carry a small metal marlinspike specifically to help pry apart a heavily loaded double fisherman's knot after use, treating the extra tool as simply part of the kit that comes with trusting this particular bend.
How to tie the Double Fisherman's Knot
Lay the two rope ends parallel, pointing in opposite directions.
Strength & security
Approx. strength retained: 65-70%
The two interlocking double overhand knots jam against each other under load and are extremely resistant to slipping, which is exactly why it's the standard way climbers join two cord ends to form a closed prusik loop or join rappel ropes.
Cautions: It's genuinely difficult to untie once it's been heavily loaded - sometimes requiring real effort or a knot tool - which is a documented reason some climbers now prefer the zeppelin bend for a rappel-rope join they expect to untie repeatedly.
Alternatives
- Triple Fisherman's Knot
Adds one more wrap on each side for extra margin on very slick, thin, or high-modulus cord where the double version's grip feels marginal.
- Zeppelin Bend
Considerably easier to untie after being loaded, which matters when the join is expected to be undone repeatedly, such as retrieving a rappel rope.
FAQ
Why is the double fisherman's knot hard to untie?
The two double overhand knots jam against each other under load, and the harder they've been loaded, the tighter that jam becomes - genuinely useful for security, genuinely inconvenient afterward.
What's it used for in climbing?
Most commonly to close a loop of cord for a prusik hitch, and to join two rope ends for a rappel, precisely because it resists slipping better than most alternatives.
Do climbers carry a tool just to untie this knot?
Some do - a small marlinspike or similar tool can help pry apart a heavily loaded double fisherman's knot, which is treated as a normal part of using a bend this trustworthy.
Should the double fisherman's knot be re-checked before each use?
Unlike a water knot in webbing, it doesn't creep the same way, but any knot joining a prusik loop or rappel rope should still be visually inspected before use for consistent dressing and adequate tail length, simply as routine equipment care rather than because this particular knot is prone to loosening.
Can the double fisherman's knot be tied with only one hand available?
It's difficult one-handed because of the multiple wraps each side requires - most climbers tie it with the rope braced against a knee or the ground rather than attempting it fully in the air with one hand occupied.