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KA

← Where the theory applies
Loop — mid-line

Bowline on a Bight

Interlock · Climbing

DiagramsHow to tie it

Does not pick a knot

This page does not pick a knot for you. DNA, molecules, quantum braids and vortices stay off Decide.

Finished structure

No drawing of this exact knot yet. The written steps are the reference.

Failure modes

When this family fails, it fails as these. The recovered end still outranks the name.

Bowline family

Fixed eye whose lock is a collar seated on the standing part.

  • !Open collar — the eye capsizes under cyclic load
  • !Cowboy / wrong-direction loop
  • !Tail too short to backup, or a Yosemite finish on an unfinished bowline
Fails when
  • !Only one loop is loaded. The knot can slip, and that loop lengthens while the other shortens.
  • !The bight is tucked through the eye but not passed over the whole knot, so it can pull back out under load.
  • !The collar sits around only one standing part or stays caught on a loop, so it does not lock the eye.
Geometry

  • Bight never encircled both standings

    One loop collapses or the knot capsizes

    The opened bight must pass around the whole knot · step 03

  • Unequal undressed loops

    One eye walks; the other takes all the load

    Both loops must be dressed after the wrap-around · step 04

  • Used for three-way mid-line load

    Structure was not built to take load on both standings plus the loops that way

    Three-way load is an Alpine Butterfly job · step 04

If you saw this

  • One loop collapses or the knot capsizes

    Check

    • ?Bight around both standing parts
    • ?Two open loops

    Then

    • →Retie and finish the wrap-around
    • →Use Alpine Butterfly for three-way load

  • Bight never encircled both standings

    Check

    • ?One loop collapses or the knot capsizes
    • ?Inspect step 03

    Then

    • →Retie. Do not dress a defective structure and call it seated.

  • Unequal undressed loops

    Check

    • ?One eye walks; the other takes all the load
    • ?Inspect step 04

    Then

    • →Retie. Do not dress a defective structure and call it seated.

  • Used for three-way mid-line load

    Check

    • ?Structure was not built to take load on both standings plus the loops that way
    • ?Inspect step 04

    Then

    • →Retie. Do not dress a defective structure and call it seated.
Same family

Same failure class, different geometry. Open the plates — Diagnose still starts from the symptom.

This failed — start Diagnose

What holds it

  • ·A mid-line loop is tied on a bight. Both standing parts stay load-bearing.
  • ·Alpine butterfly and bowline-on-a-bight are different geometries for the same job class. Invariants do not rank them.

What topology does not predict

  • ·Direction of pull (one standing part vs both) is mechanics, not knot type in the Jones sense.
  • ·No working-load table is attached here.
  • ·Capsizing under ring load is a physical defect, already a Diagnose story.

Not for

  • ·An end-of-line terminal eye
  • ·Using this page to override a Decide elimination
  • ·A single end-loop (use a bowline)
  • ·A mid-line loop that must take three-way load (use Alpine Butterfly)

Same pattern, different job

Sources