Reef Knot
Binding / reefing only. Two nested half-knots. Must never be offered as a rope-to-rope join.
Beginner · Polyester / Nylon rope / Polypropylene / Natural fibre
Connection card
Reef Knot
For reef / bind.
This card does not say how strong the knot is. A retention figure comes from a bench, in one material, at one diameter, tied by somebody who ties it all day — and the line in your hand is none of those. What it does tell you is whether the thing you have just tied is the thing the record describes.
What this plate is telling you
Binding / reefing only. Two nested half-knots. Must never be offered as a rope-to-rope join.
Save this as a picture and it works with a dead signal and a nearly dead battery, which is when a joint is most often tied badly. The rest of this page — the steps, the seating sequence, the failure modes and the bench — is for the evening before.
Why this knot
What it earns its place with, what it costs, and what to reach for instead.
- Joining two ropes (it slips as a join)
- Unequal diameters
- Any life-critical or standing load
- Crossing the same way twice, which makes a granny knot
- Using it to join two ropes that will each take load
- Pulling on one end only when drawing it down on the bundle
- Tying it with ropes of different thickness
- Constrictor KnotIntermediate
A bind that must not walk
- Sheet BendBeginner
Join two ropes of unequal or similar diameter
Before you start
- ·Use it to bind a sail or bundle. Animated Knots warns against using it as a bend to join two ropes, or for critical loads.
- ·Either end can go over first. The second half knot has to cross the opposite way to the first, or the result is a granny knot.
- ·Use two ends of the same thickness. With ropes of different sizes, tie a different knot.
- ·Leave the ends long enough to grip, and let the load come on the bundle rather than on the two ropes pulling against each other.
Step 1 of 4 · move 1 of 2. Pass both ends round the bundle and cross the left (orange) end over the right
Space plays or pauses. Keys 1, 2, 3 and 4 set the speed. Arrow keys change the move.
swipe to step
01.1
Pass both ends round the bundle and cross the left (orange) end over the right
- Hold:
- Right hand holds the right (dark) end up against the bundle
- Move:
- Left hand lays the left (orange) end across the front of the right end
Pass both ends around the sail or bundle, cross the left end over the right, and tuck it under and up.
One half knot snug against the bundle, with an end coming up on each side.
Starting a reef knot to join two ropes that will each take load. Pulled end to end it can capsize and come apart.
Fix: To join two ropes, tie a bend such as a sheet bend instead, and keep the reef knot for binding.
Why: Either end can go over first. What matters is that the second half knot is the reverse of this one.
- Used as a rope-to-rope join — Capsizes and slips under standing load. Animated Knots: always a binding knot at sea — never a bend.
arrow keys work
Tying procedure — Reef Knot
Step 01 / 4
Pass both ends around the sail or bundle, cross the left end over the right, and tuck it under and up.
You should now see: One half knot snug against the bundle, with an end coming up on each side.
If it goes wrong: Starting a reef knot to join two ropes that will each take load. Pulled end to end it can capsize and come apart.
Fix: To join two ropes, tie a bend such as a sheet bend instead, and keep the reef knot for binding.
Why: Either end can go over first. What matters is that the second half knot is the reverse of this one.
Step 1 of 4 · move 1 of 2
Pass both ends round the bundle and cross the left (orange) end over the right
Hold: Right hand holds the right (dark) end up against the bundle
Move: Left hand lays the left (orange) end across the front of the right end
Step 1 of 4 · move 2 of 2
Tuck the left end under the right end and bring it up: one half knot
Hold: Right hand holds the dark end where the two cross
Move: Left hand takes the orange end down behind the dark end and up, then snugs it
You should now see: One half knot snug against the bundle, the orange end now coming up on the right and the dark end on the left.
Step 02 / 4
Cross the end now on the right over the left end and tuck it under and up. It is the same rope that went on top in the first half knot.
You should now see: Each rope's end lying alongside its own standing part, forming two collars that nest together.
If it goes wrong: Crossing the same way twice, left over right again. That makes a granny knot, and its ends come out across the standing parts instead of alongside them.
Fix: Undo the second half knot and cross the other way.
Why: Animated Knots notes the granny is often tied by mistake and holds even worse than the reef knot.
Step 2 of 4 · move 1 of 2
Cross the end now on the right over the left end: the orange end on top again
Hold: Left hand brings the dark end up and across to the right
Move: Right hand brings the orange end back to the left, over the dark end
- 1Orange end beside orange standing part2Dark end beside dark standing part
Step 2 of 4 · move 2 of 2
Tuck the orange end under the dark end and up, out beside its own standing part
Hold: Left hand holds the dark end and the first half knot
Move: Right hand takes the orange end under the dark end and up, and lays it out left
You should now see: Each end lying alongside its own standing part: orange out on the left beside orange, dark out on the right beside dark, the two bights nested.
Step 03 / 4
Pull both ends evenly to draw the knot down flat on the bundle.
You should now see: A flat, symmetrical knot lying on the bundle, with each end and its standing part still side by side.
If it goes wrong: Pulling on one end only, or tying ropes of different thickness. One rope pulls straight and the other slides along it as a loop, which means the knot has capsized.
Fix: Work the knot back into two flat loops and pull both ends evenly. If the ropes differ in size, tie a different knot.
Why: The two half knots hold by pressing on each other against the bundle. Once one rope pulls straight, nothing locks the other.
1Orange end and standing part side by side2Dark end and standing part side by sideStep 3 of 4 · move 1 of 1
Pull both ends evenly to draw the knot down flat on the bundle
Hold: Left hand pulls the orange end and its standing part together
Move: Right hand pulls the dark end and its standing part the same amount
You should now see: A flat, symmetrical knot on the bundle, each end still lying beside its own standing part.
Step 04 / 4
Leave the ends long enough to grip, and put the load on the bundle the knot binds rather than on the two ropes pulling against each other.
You should now see: The knot stays flat and unchanged when the bundle shifts, with the ends still alongside their standing parts.
If it goes wrong: Relying on it where a slip would drop a load or put someone at risk. Animated Knots warns against using the reef knot for critical loads.
Fix: Keep it for sail ties and bundles. Where the load matters, tie a knot made for that job.
Step 4 of 4 · move 1 of 1
Leave the ends long and let the bundle take the load, not the two ends
Hold: Both hands leave the ends long enough to grip
Move: The load goes on the bundle the knot binds, never end pulling against end
You should now see: The knot stays flat and unchanged as the bundle shifts, with the ends still beside their standing parts.
What this is based onReference review, not yet tied · 1 known limit
- Record
- Reviewed 2026-08-14. 2 sources are cited for this record.
- Drawing
- Checked against published references and found to be this knot. Not yet tied from the drawing. Recorded 2026-09-21.
- Older drawing
- An older drawing of this knot is withdrawn and shown nowhere. The audit's reason: No over/under at any crossing, so the drawing is equally a granny knot, which slips. A reef is defined by which way each half crosses.
- Strength
- 50% of the weaker line, manila rope up to 1" diameter, from an efficiency table credited to The Art of Knotting and Splicing (United States Naval Institute) and reprinted with no test data behind it; the figure is for the knot loaded as a bend, which is the use every publisher warns against. Instructor consensus — International Guild of Knot Tyers — Solent Branch. No published break test is cited; the band is where instructors agree, not a measurement.
What the drawing does not show
- Step 2, move 2 of 2: The tuck happens behind the dark strands; only a short piece of the orange end shows.
Watch the tie
Drawn from this knot's sequence — the same rope as the steps. Not a recording of hands. It does not start until you press play.
Another recording
How to Tie a Square Knot (Reef Knot)AnimatedKnots · Opens on YouTubeAn outside recording of this construction. It is not the drawing above, and nothing here loads from YouTube until you follow the link.
Seating sequence — where failures are born
The step list compresses the finish. Run these phases in order, one at a time.
01 Form
Build the structure loose enough to see every turn.
None. Shape first.
02 Dress
Nest every turn. Crossed parts will walk or jam.
Light — hold the shape.
03 Set
Load the standing part so the intended turns take the strain.
Working load, not a snatch.
04 Check
Confirm the lock still breaks or inspects as the job requires.
None extra.
05 Commit
Only load it after the structure reads correct. Wrong means remake.
Working load, not a snatch.
Finished structure — what correct looks like
Drawn from a rope model of this knot: which strand passes over which comes from where the rope actually lies.
- Structure
- Left-over-right then right-over-left (or the reverse pair); two nested half-knots sitting flat around the sail or bundle
- Standing line
- Binding a reef or bundle. If the two standing parts will take load as a join, this will slip
- Tag end
- Both ends leave the flat nest — standing parts are not a join
- Wraps
- Two opposite-hand half-knots — same hand twice is a granny
- Seating
- Pull both ends so the knot sits flat. A capsized reef is already failing
Verify before you load it
Every line is pass or fail. One fail means retie — do not load a knot you argued with.
- 01Left-over-right then right-over-left (or the reverse pair); two nested half-knots sitting flat around the sail or bundle
- 02Pull both ends so the knot sits flat. A capsized reef is already failing
- 03Both ends leave the flat nest — standing parts are not a join
- 04Two opposite-hand half-knots — same hand twice is a granny
- 05Same-hand twice, or used as a join, spills
- 06Flat bind only. Need a join? Sheet bend or Zeppelin
Field notes — dark, cold, gloves
- ·Dress is the lock. A pretty knot that is not dressed is not finished.
- ·HMPE usually wants a splice, not a hitch you learned in polyester.
- ·If you cannot break or inspect it under the load you expect, it is the wrong job.
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.
Get it right with everything in your favour0/5 clean
Nothing logged on this knot yet, so it starts on the bottom rung.
Good light, dry hands, a table. Until the sequence is automatic here there is nothing for the harder rungs to test — you would only be learning that difficult conditions are difficult, which you already knew.
How · Tie it, check it against the list, log it. Five clean and the ladder opens.
Nothing marked. Log it clean, or mark what happened first.
Strength, and where the number comes from
50% of the weaker line
Instructor consensusmanila rope up to 1" diameter, from an efficiency table credited to The Art of Knotting and Splicing (United States Naval Institute) and reprinted with no test data behind it; the figure is for the knot loaded as a bend, which is the use every publisher warns against
Knot Strength Chart — International Guild of Knot Tyers — Solent Branch
Percentages come from published tests on their own line, their own knot-tyer and their own pull rate. Yours is a different system. Treat a figure as a reason to test, not as a result you already have.
- 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.
Record reviewed 2026-08-14
Vetted references
- Animated Knots — Square (Reef) Knot
Animated Knots by Grog
- How to Tie a Square Knot (Reef Knot)
AnimatedKnots
Take the Foundation quiz — can you recognise this knot's finished state and failure modes?
Related knots
Check the finished knot against what correct looks like before you load it.