How to Tie the Impossible Knot

By: Melanie Radzicki McManus
The impossible knot
The impossible knot is not impossible to tie — it's impossible to untie!
Scott Cramer/iStock/Thinkstock

Many people think the only knot they need to know how to tie is the one used to tie shoes. That's a bowknot, by the way. Or, to us common folks, bunny ears. But knots come in handy for many more things. Fishermen use a wide variety of knots to fasten everything from nets to boats. Climbers need knots for scaling up mountains — a poorly knotted line can result in injury or even death. And then there are cowboys, farmers and cargo-haulers. The times a good, strong knot can come in handy are limitless.

So what's the best knot of all? There isn't one. It all depends on what you'd like the knot to do. Do you want it to secure something tightly or loosely? Do you want to lash items together or fashion a knot that's adjustable? Sometimes it's handy for a knot to be secure, yet able to release quickly. And what about a knot's complexity? If you can't tie the thing easily, is it really so great?


Pretty much anyone can master the art of knot-tying. Even when it comes to the impossible knot. The impossible knot isn't its technical name; it's actually a nickname for the double fisherman's knot. And it got this name not because it's impossible to tie — it's actually quite easy — but because it's nearly impossible to untie.

The double fisherman is a knot used to tie two ends of a rope or cord together. Actually, it's two knots that slide together. Over time, the knots sort of seal themselves as one, and often the only way to undo the thing is to cut the knots out. Interestingly, the double fisherman's knot is rarely used in fishing. It's common in climbing and other sports. Kayakers and canoeists, for example, sometimes use it with short pieces of rope to create grab handles for their watercraft [source: NetKnots]. So how did it get the name "double fisherman"? Since it's easy to tie, it works well on small lines, such as fishing line [source: Indoor Climbing]. Ready to learn how to tie one?


Instructions for Tying the Double Fisherman's Knot

So you're not too scared to try the double fisherman's knot? Remember, only proceed if you're joining two pieces of rope or cording that you'd like to stay permanently tied. Here's how to do it:

Instructions for tying the impossible knot.
© HowStuffWorks 2015
  1. Set your two pieces of rope side by side. For ease of explanation, let's assume one is gold and the other is blue.
  2. Take one end of the blue rope and wind it loosely twice near the end of the gold rope.
  3. Now take the blue rope and pull it back through the inside of the loops or coils that you've just created and pull to tighten. That's one knot.
  4. Now take the short end of the gold rope, and pull a little to give yourself more rope to work with. Take that lengthened gold rope and repeat the earlier steps, only wind the gold rope in the opposite direction than you'd wound the blue rope. So if you started winding the blue rope by moving it over the gold rope, take the blue rope and start winding it by moving it under the blue rope.
  5. After you've created and tightened the second knot, pull each rope's main ends (not the short ends by the knots), and the two knots will slide together. Voilà!

If you've properly tied a double fisherman's knot, each knot should have an X on the same side. The other side should show four neat rows of wound cord [sources: A Site About Nothing, Net Knots, YouTube].



Other Impossible Knots

Person sitting on boat
Althought double fisherman's knot is called the "impossible knot," it’s seldom used by fishermen. Kayakers and canoeists are more likely to use it.
© Richard Baker/In Pictures/Corbis

The double fisherman's is one tough knot, it's true. But so is the constrictor (as in boa). Also called a gunner's knot, whip knot and timber knot, this particular knot is used to bind a rope very tightly to an object, such as tying a boat to a pole. If you'd like to tie a constrictor over something soft, the knot will hold better if you use a hard, stiff cord. If you intend to tie it over a hard surface, in contrast, a soft, stretchy one is best [source: Knots 3D].

Like the double fisherman's, the constrictor is a really difficult knot to untie. In some cases, it may be impossible, especially if you used a small line. In that case, the knot's binding force is concentrated over a smaller area, which gives it an extra hard bite. Sometimes, the knot can damage or scar the item it's tied around. If the constrictor doesn't sound ominous enough, there's also a double constrictor -- basically the same knot tied twice. Yes, it's even harder to untie [source: Knots 3D].


Another knot that can be difficult to loosen is the figure 8 loop. This knot is often used in climbing to secure the climber to the rope through his harness. If the climber falls, it's the figure 8 loop that will stop him from smashing into the ground (assuming it's tied properly). So it's a good thing it is hard to untie [source: Climbing Knots].

Are there any knots that are easy to undo? Certainly the bowknot, the one you tie your shoelaces with, is. But there's a knot that's made specifically to be easily loosened, and that's the highwayman's hitch. This simple, quick-release knot is used when tying up a horse, for example. The knot was supposedly given its name centuries back, when bandits — then known as highwaymen — tied up their horses with these knots when they ran off to quickly loot a spot [source: Action Donation Services].


Boy Scout Knots

To many, knots are synonymous with the Boy Scouts. And for good reason: The Boy Scouts movement began in England, courtesy of a chap named Robert Baden-Powell. Baden-Powell was a famous British war hero who wrote a military field manual called "Aids to Scouting." Young boys discovered this book and found its lessons on tracking and observation fascinating. So Baden-Powell penned another book, "Scouting for Boys," aimed at this younger audience. That book, published in 1908, was the start of the Boy Scouts [source: History].

"Scouting for Boys" contained information on activities like camping, woodcraft, boating and lifesaving. It's here that the necessity of learning various knots came into play — a whole chapter was devoted to saving lives with knots. Additionally, the book taught the importance of morality, chivalry, patriotism and good deeds [source: History].


Britain's sailing. Still, many scouts there and in other parts of the world do learn how to tie many knots during their years in the organization. Here are six of the more common knots American Scouts are taught [sources: Boy Scout Trail, Boy Scouts of America]:

  • Square knot. Simple binding knot that can be used on shoes or for holding a pad on a wound. It's the first knot boys learn when they join the Scouts,
  • Bowline. Called the "king of knots"; used to make nonslip loop at end of a rope
  • Sheet bend. Good for tying two ropes together
  • Clove hitch. Used with stiff, thick ropes; good for lashing together two poles; required for rowing merit badge
  • Two half hitches. Versatile binding or hitch knot; required for rowing merit badge
  • Tautline hitch. Adjustable knot used in tent guy lines; required for canoeing merit badge


Impossible Knot FAQ

What is the hardest knot to untie?
The constrictor knot is one of the hardest knots to untie once it's secured in place.
Which knot tightens as you pull?
The Arbor Knot is based on a noose knot. Therefore, it tightens further when you try to loosen it.
How do you undo an impossible knot?
One of the most effective ways to untie a difficult knot is to twist the end of it. As it constricts, push it further to the rest of the knot.
What is the weakest knot?
The clove hitch is the weakest and easiest knot to untie.
Is the Gordian knot real?
Greek legend says that the Gordion knot is, indeed, real. It was one of the most stubborn knots in history and could not be untied no matter how hard people tried. In the end, Alexander the Great solved it by cutting through it with a sword.

Lots More Information

Author's Note: How to Tie the Impossible Knot

I've never been good with knots. Actually, the only one I know how to reliably tie is the good old bunny ears. But I'd like to take a stab at the double fisherman's. I just need to find two things I can tie together that can remain tied for eternity!

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More Great Links

  • A Site About Nothing. "Andy's Most Useful Knots." (May 11, 2015)
  • Animated Knots By Grog. "Constrictor Knot (Twisting Method)." Nov. 24, 2014. (May 11, 2015)
  • Bisharat, Andrew. "The Seven Need-To-Know Climbing Knots." Backcountry. May 6, 2015. (May 11, 2015)
  • Boy Scouts of America. "Canoeing." (May 13, 2015)
  • Boy Scout Trail. "Scout Requirements Study Guide." (May 13, 2015)
  • Boy Scouts of America. "First Class Rank Requirements." (May 13, 2015)
  • Boy Scouts of America. "Pioneering." (May 13, 2015)
  • Boy Scouts of America. "Rowing." (May 13, 2015)
  • Climbing Knots. "How to untie a Figure eight Loop." (May 14, 2015)
  • De Decker, Kris. "Lost knowledge: ropes and knots." Low-Tech Magazine. (May 11, 2015)
  • Geffre, John. "The Six Boy Scout Knots." Merit Badge. Aug. 20, 2001. (May 12, 2015)
  • History. "Boy Scouts movement begins." (May 20, 2015)
  • Indoor Climbing. "Tie the Fisherman's Knot." (May 17, 2015)
  • Knots 3D. "Constrictor Knot." (May 11, 2015)
  • NetKnots. "Constrictor Knot." (May 11, 2015)
  • NetKnots. "Double Fisherman's." (May 11, 2015)
  • RopeBook. "Knot History." (May 11, 2015)
  • The Telegraph. "Modern scout leaders 'don't need to know how to tie knots.'" Nov. 2, 2014. (May 20, 2015)
  • Titan Paracord. "Constrictor Knot." Oct. 1, 2014. (May 11, 2015)
  • YouTube. "The Impossible Knot." Sept. 1, 2009. (May 11, 2015)