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KA

← Where the theory applies
Loop — fixed

Figure-8 Loop

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.

Figure-8 Loop, finishedFigure-8 Loop, finished

Finished structure

Drawn from a rope model of this knot: which strand passes over which comes from where the rope actually lies.

Failure modes

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

Figure-eight loop family

Nested eights in a bight — inspectable, stable, and they jam after a snatch.

  • !Crossed eight that will not dress
  • !Eye eaten by the eight because the loop was sized after the set
  • !Expected to untie after a hard snatch
Fails when
  • !Heavily loaded, after which it can jam and be hard to untie
  • !Loaded before dressing, with the strands twisted or crossed
  • !Outer turns left loose instead of snug against the strands they enclose
Geometry

  • Crossed eight

    Weaker, hard to inspect, may not dress

    Both strands must nest through the same eight · step 02

  • Eye eaten by the eight

    Loop smaller than the post or too small to use

    Eye size is decided in the bight before the eight · step 01

  • Expected to untie after a snatch

    Jammed eight, knife job

    This eye trades release for stability · step 04

If you saw this

  • Loop distorts or the eight will not dress

    Check

    • ?Nested eights
    • ?Both strands parallel

    Then

    • →Untie and retie a clean eight

  • Crossed eight

    Check

    • ?Weaker, hard to inspect, may not dress
    • ?Inspect step 02

    Then

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

  • Eye eaten by the eight

    Check

    • ?Loop smaller than the post or too small to use
    • ?Inspect step 01

    Then

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

  • Expected to untie after a snatch

    Check

    • ?Jammed eight, knife job
    • ?Inspect step 04

    Then

    • →Retie. Do not dress a defective structure and call it seated.
This failed — start Diagnose

What holds it

  • ·A fixed loop is a standing eye. The collar or figure-eight body must survive a straight pull without becoming a noose.
  • ·Bowline and sheet bend are the same crossing pattern under different load. That identity is seamanship, not a reason for Decide to swap one for the other.

What topology does not predict

  • ·Fixed vs slipped is a load-path question. Invariants do not choose bowline over figure-eight.
  • ·Ring-loading and slack-shaking failure are physical. Topology does not grade them.
  • ·No UIAA or manufacturer number is inferred here.

Not for

  • ·A lure that must swing on a non-slip loop — this standing eye is a different job
  • ·Letting a climbing identity pick your fishing knot
  • ·A loop you must untie after a hard snatch (it can jam)
  • ·Fairlead-critical running rigging

Same pattern, different job

Sources