Key takeaways
- The double fisherman's joins two ropes/cords with two interlocking double overhand knots.
- It's strong, secure, and resistant to slipping — a trusted bend.
- Standard for tying cord into permanent loops (prusik loops, cordelettes) and joining rappel ropes.
- Its main drawback: it's very hard to untie after being heavily loaded, so it's often left permanent.
What the double fisherman’s is
The double fisherman’s knot (or grapevine knot) is a strong, secure bend — a knot for joining two ropes or cords — formed by two interlocking double overhand knots that cinch against each other when loaded. It’s one of the most trusted joining knots in climbing.
What it’s used for
- Tying cord into closed loops — its most common use, making prusik loops and cordelettes.
- Joining two rappel ropes for a longer descent.
- Backing up other knots.
To make a prusik loop, a climber takes a length of accessory cord and ties its two ends together with a double fisherman’s — dressing the two knots so they seat neatly together — creating a strong, permanent loop they’ll use for friction hitches.
Its one drawback
After heavy loading, the double fisherman’s becomes very hard to untie, as the two knots lock against each other. So it’s best used where the join can be permanent — like a prusik loop — rather than where you’ll need to undo it. Where easy untying matters, climbers pick other bends, just as the figure-eight is preferred for its inspectability when tying in.
The bottom line
The double fisherman's is the climber's go-to knot for joining cords and ropes — two interlocking double overhands that lock into a strong, secure bend. It's the standard for making permanent loops like prusik loops and cordelettes. Just know its one catch: after heavy loading it's a beast to untie, so reserve it for joins you don't need to undo.
Frequently asked questions
What is the double fisherman's knot used for?
It's used to securely join two ropes or cords together. In climbing, its most common use is tying a length of cord into a closed loop — like a prusik loop or a cordelette — and it's also used to back up other knots and to join two rappel ropes. Its strength and security make it a go-to bend.
How does the double fisherman's knot work?
It consists of two double overhand knots, each tied around the other rope's standing end, which then slide together and lock against each other when loaded. The two interlocking knots grip tightly and resist slipping, making the join very secure. Dressing it neatly (so the strands lie parallel and the knots seat together) is important for full strength.
What's the downside of the double fisherman's knot?
It becomes very difficult to untie after being heavily loaded, because the two knots cinch hard against each other. For this reason it's typically used where the join can be permanent — like a sewn-shut prusik loop — rather than where you'll need to undo it. Where easy untying matters, climbers often choose other bends.
Sources
- Climbing knots — American Alpine Club
- Knots & rope work — The Mountaineers