Note: when used in "human fall protection” / climbing applications, the common bowline as shown below is NOT considered safe unless it has been secured in some way. This is typically done with a stopper knot in the tail or a Yosemite finish. (Having said that, knowing how to tie a bowline is helpful in many different non-climbing applications, even the “simple” version shown here so it's still a great knot for the tool kit.)
If you want a deep dive into proper application of knots, the Australian Professional Association of Climbing Instructors (PACI) website is a great place to start.
Ah yes, the bowline knot. A favorite of sailors, Boy Scouts, and sometimes climbers, commonly used to tie the free end of the rope around a boulder or tree as a fixed line, or possibly stringing up a tarp.
However, for some reason, this knot is deceptively difficult for many people to tie correctly. (I’ve seen otherwise very experienced climbers screw this knot up on many occasions.)
Many people seem able to tie it properly in a somewhat controlled setting, like practicing it around a table leg. But put them on the other side of the rope, or make them tie it facing a different direction than usual, or some other minor switcheroo, and “knot dyslexia” seems to set in. And, to be honest, I’ve experienced this myself a few times.
Well, I recently learned very cool way to tie a bowline that seems to solve all these issues. It’s fast, reasonably idiot proof, and most people find it much easier than the old-school “rabbit comes out of the hole, around the tree and back into the hole” method. And, as with some of the best rope techniques, and there is a bit of rope magic happening that would make you blink and say “Dang, did I just really see that?!” (It turns out this method was first described in 1914, so like I said, new to me but not new!)
Pass the end of the rope around your anchor object, here a post.
2) Make a slipknot.
3) Pass the end of the rope through the loop of the slipknot. (Keep the slip knot and loop fairly loose, as you see here.)
4) Tighten the slipknot. It will invert and makes a “snap”, then you should magically have a bowline.
Yes, you need to try this a few times at half speed to see this sorcery for yourself, it really is sort of a magic trick!
Note: depending on how you feed the free end through the slipknot, the final version of your bowline could be in one of two configurations.
One, you may end up with the free end inside of the loop (as we see above) which is the standard garden-variety bowline. Or, you may end up with the free end outside of the loop, which is known in some circles as a “cowboy bowline.” One is not conclusively stronger / better / preferable to the other, so it appears not to really matter which way the tail ends up. You can read more on this discussion here.
“Standard” bowline on left, “cowboy” bowline on right. “b” is the load, “a” is the free end.
As we like to say at Alpine Savvy, most any sort of hands on skill like learning a knot is a better show than a tell.
Here are two short videos that shows you exactly how to do it. Go get some cord and try this a few times, and you’ll be a convert.
I think you need to watch the first video in another browser tab, but it's worthwhile. It shows you how to tie it in a pretty slick (mostly) one-handed method.
and here is an example of why a bowline and is not recommended for critical load support. (Yes, this is a large diameter rope, and yes it is tied too loosely and not dressed, but it's still an interesting demonstration.)