Bowline on a Bight
loop 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.
Riggers and sailors reach for the bowline on a bight in exactly the situation where the plain bowline can't help: there's no free rope end to work with, only a closed loop of rope (a "bight"), and a fixed double loop is needed anyway. The trick is to tie the first stage of an ordinary bowline using the folded bight as if it were a single working end, then open that bight out and fold it back over the whole knot instead of tucking it through - the result is two loops that share one collar and can each be loaded independently.
This is the traditional "boatswain's chair" knot: one loop goes around each thigh, or one around the body and one under the arms, and a person can be lowered or hauled with a reasonable seat even without a harness. It has also seen use as an improvised rescue loop when a stranded person's legs go through the two loops and the collar sits at the waist.
Because it's still fundamentally a bowline, the same capsizing risk under repeated slack-tight loading applies, and it inherits the bowline's dependence on even dressing. The extra complexity of getting both loops truly equal in length is the main practical hurdle - a rushed tie in an emergency can load one loop far more than the other.
Because both loops share a single collar, the knot also sees occasional use anywhere two separate attachment points are needed from the same rope without cutting it - hoisting an awkward load with two sling points, for example. Riggers who tie it regularly note that the folding step, where the bight is opened out and folded back over the entire first-stage knot, is the one most beginners get backwards; folding it the wrong way produces a knot that looks similar but doesn't hold its shape as reliably under an uneven pull.
How to tie the Bowline on a Bight
Fold the rope to form a bight (a doubled section with no end) and tie the first part of a bowline using the bight as if it were a single working end.
Strength & security
Approx. strength retained: 60-70%
Shares the standard bowline's core geometry, so it holds a steady pull well but can be worked loose by the same slack-tight cycling; the doubled loops distribute a seat or harness load across two strands rather than one, which is its real advantage over a single bowline in a rescue seat.
Cautions: Both loops must be dressed evenly - if one loop is even slightly shorter, nearly all the load transfers to it under weight. Not a substitute for a rated climbing harness in anything but an improvised emergency.
Alternatives
- Bowline
Simpler and faster to tie when only one loop, not two, is actually needed.
- Alpine Butterfly Loop
Ties a mid-line loop without needing to fold the rope into a bight first, and can take load from either standing part - useful when both rope ends are already committed elsewhere.
FAQ
Can the bowline on a bight replace a climbing harness?
Only as a last-resort improvisation. It distributes load across two loops reasonably well but has none of a harness's padding, adjustability, or fall-rated hardware.
Does it need two rope ends?
No - that's the entire point of the knot. It's tied entirely from a bight (a folded section of rope), so it works even when both actual ends are inaccessible or already in use.
What's the most common mistake when tying this knot?
Folding the large loop the wrong way over the first-stage knot - it looks similar either way, but only the correct fold produces two loops that hold their shape under an uneven pull.
Is the bowline on a bight used in any modern rescue standard?
Yes - many wilderness and confined-space rescue courses still teach it as a fallback improvised seat when no rated harness is available, precisely because it can be tied from rope alone in under a minute by someone who already knows a standard bowline. It should never replace a certified harness where one is available, but as a stopgap during an unplanned rescue, its two load-bearing loops give meaningfully more security than a single loop or an improvised sling would.