Falling from the top of a rock face with only a thin rope standing between you and oblivion is an unnerving experience made somewhat less so by the extreme reliability of modern climbing gear. "The system works," we tell ourselves, moments before plunging groundward from the top of a sport route or an indoor wall. And it does work, except for when it doesn't.

On November 29, Yosemite climbing legend John Long was seriously injured in an accident at a Los Angeles gym when his bowline knot came undone. He fell to the floor, sustaining a compound fracture that tore through the skin of his ankle. Two surgeries later, Long is recovering, but he still faces more hospital time and a long stint in physical therapy; friends have set up a donation page to defray his out-of-pocket expenses.

How did John Long, who was a member of the party that made the first one-day ascent of the Nose and wrote a series of books titled How to Climb, manage to nearly end himself in a gym? Long himself attributes the accident to human error. Speaking to Rock and Ice, he admitted he forgot to finish tying his knot. "I screwed up big," Long said.

But there's another culprit in this story: the bowline knot itself.

Regardless of what your crusty climbing partner says, using the bowline knot you learned in Boy Scouts to connect yourself to a rope is asking for trouble. Climbers who prefer to tie in with a double bowline instead of the standard figure-eight follow-through almost universally point to the ease of untying a bowline after a fall. Unfortunately, they usually miss the obvious corollary, that the bowline has a way of working itself loose if not backed up properly, which is pretty much the exact opposite of what you want in a knot your life depends on.

The bowline is also more complex than the figure-eight, which means it's easier to screw up and harder for a partner to check visually. This is the mistake that injured Long and killed David Rothman, a 73-year-old British climber who fell to his death in April.

"Know the bowline for what it is: An instrument of death," Rock and Ice's Duane Raleigh wrote in a blog post after the release of this year's Accidents in North American Mountaineering in September. "Almost every year someone dies because their bowline either came untied because the complicated knot was tied wrong, or because the bowline magically untied itself."

It's true that, carefully tied and tightened, a bowline can be a fairly safe tie-in knot, and it's tempting to think, I won't make their dumb mistake. But it's also true that many, if not most, rock climbing fatalities are the result of "dumb mistakes," whether that's clipping into a carabiner that's not secured to the anchor or rappelling off the end of a rope. No one is immune to the occasional lapse, not even a master like John Long, so it makes sense to use a system that is as foolproof as possible.