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Diagram

Reef Knot

Square knot · Reef

Binding two ends of the same line around a sail or bundle. Animated Knots warns against using it to join two ropes or for critical loads.

Binding · Beginner · Polyester / Nylon rope / Polypropylene / Natural fibre · 4 steps

ApplicationsHow to tie it
Reef Knot, finishedReef Knot, finished

Finished structure

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

  1. Pass both ends round the bundle and cross the left (orange) end over the rightThe rope goes round behind the bundle and both ends come to the front: the left end, orange, comes in from the left and crosses over the right end, dark.
    Move 1 of 2Pass both ends round the bundle and cross the left (orange) end over the right
    Tuck the left end under the right end and bring it up: one half knotThe orange end has gone over the dark end and then under it and up, making one half knot on the bundle; the orange end now comes up on the right and the dark end on the left.
    Move 2 of 2Tuck the left end under the right end and bring it up: one half knotYou 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 01

    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.

  2. Cross the end now on the right over the left end: the orange end on top againAbove the first half knot the orange end, now coming from the right, crosses over the dark end, which comes from the left. The same rope is on top as in the first half knot.
    Move 1 of 2Cross the end now on the right over the left end: the orange end on top again
    Tuck the orange end under the dark end and up, out beside its own standing partThe orange end has gone under the dark end and up, so it leaves on the left beside its own standing part and the dark end leaves on the right beside its own. Each rope makes one U-shaped bight and the two bights interlock.
    1Orange end beside orange standing part
    2Dark end beside dark standing part
    Move 2 of 2Tuck the orange end under the dark end and up, out beside its own standing partYou 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 02

    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.

  3. Pull both ends evenly to draw the knot down flat on the bundleThe reef knot drawn down flat on the bundle: an orange bight and a dark bight interlocked, orange end and standing part leaving together on the left, dark end and standing part together on the right.
    1Orange end and standing part side by side
    2Dark end and standing part side by side
    Move 1 of 1Pull both ends evenly to draw the knot down flat on the bundleYou should now see: A flat, symmetrical knot on the bundle, each end still lying beside its own standing part.

    Step 03

    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.

  4. Leave the ends long and let the bundle take the load, not the two endsThe finished reef knot binding the bundle: two interlocked bights lying flat, the ends left long and each lying beside its own standing part, the rope taking the load round the bundle.
    Move 1 of 1Leave the ends long and let the bundle take the load, not the two endsYou should now see: The knot stays flat and unchanged as the bundle shifts, with the ends still beside their standing parts.

    Step 04

    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.

Failure modes

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

Bind / drag family

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
Fails when
  • !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
Geometry

  • 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

If you saw this

  • 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 family

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

This failed — start Diagnose

Why this knot

What it earns its place with, what it costs, and what to reach for instead.

Best for
Reefing or binding
Not ideal for
  • Joining two ropes (it slips as a join)
  • Unequal diameters
  • Any life-critical or standing load
Common mistakes
  • 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
Alternatives

Related knots