Reef Knot
Interlock · Constriction · Surgery
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
Drawn from a rope model of this knot: which strand passes over which comes from where the rope actually lies.
When this family fails, it fails as these. The recovered end still outranks the name.
A binding that holds two parts, or a hitch that tightens as you drag.
- !Reef knot used as a bend — it spills
- !Granny form (both tucks the same way)
- !Timber hitch with too few wraps on the object, so it walks
- !The two ropes are pulled end to end as a join, so the knot capsizes and comes apart
- !One end is pulled harder than the other, so one rope pulls straight and the other slides along it as a loop
- !The two ropes differ in thickness, which lets the knot capsize
- !Both half knots cross the same way, making a granny knot, which Animated Knots says holds even worse
Used as a rope-to-rope join
Capsizes and slips under standing load
Animated Knots: always a binding knot at sea — never a bend · step 01
Granny — same hand twice
Will slip as soon as the reef takes strain
Second half-knot must reverse the first · step 02
Capsized or unequal-diameter bind
Already failing as a reef
The knot must sit flat on similar ends · step 03
Knot capsizes and slips under standing load
Check
- ?Flat nested half-knots
- ?Binding a reef or bundle, not joining two ropes
Then
- →If you needed a join, retie a sheet bend or Zeppelin
- →If you needed a bind, retie left-right then right-left
Used as a rope-to-rope join
Check
- ?Capsizes and slips under standing load
- ?Inspect step 01
Then
- →Retie. Do not dress a defective structure and call it seated.
Granny — same hand twice
Check
- ?Will slip as soon as the reef takes strain
- ?Inspect step 02
Then
- →Retie. Do not dress a defective structure and call it seated.
Capsized or unequal-diameter bind
Check
- ?Already failing as a reef
- ?Inspect step 03
Then
- →Retie. Do not dress a defective structure and call it seated.
Same failure class, different geometry. Open the plates — Diagnose still starts from the symptom.
What holds it
- ·Reef / square is a binding knot around a parcel. Opposite-direction throws lock; same-direction throws are a granny and walk.
- ·Johanns et al. (2023) locate that difference in friction, geometry and plastic set — not in crossing count. Granny is not among these knots.
What topology does not predict
- ·Reef is not a bend for two working ropes under load. Seamanship already forbids that job.
- ·Surgical throw security is not a Palomar rating.
- ·No suture-material number is copied onto nylon dock line.
Not for
- ·Joining two ropes as a bend — use a sheet bend or a recognised bend family
- ·Letting a surgical paper pick your fishing knot
- ·Joining two ropes (it slips as a join)
- ·Unequal diameters
Same pattern, different job
No sourced twin among these knots. Related knots stay on the Library card.
- Johanns et al. — Strength of surgical knots (Sci. Adv., 2023) — Square vs granny is friction, geometry and plastic set — not crossing count.
- Reef knot (Wikipedia) — Binding knot. Capsizes. Opposite-throw pair is the granny — not in these knots.
- EPFL — Mechanics of the ideal surgical knot (2023) — Public summary of Johanns et al. Alternating throws lock; same-direction throws walk.
- Animated Knots — Square Knot (Reef Knot) — Binding / reefing only. Must never be used as a rope-to-rope join.
- AnimatedKnots — How to Tie a Square Knot (Reef Knot) — Cited tying video already attached to this record.