Binding knotBeginner

Reef knot

Get to know Reef knot: what it does, when to use it, what to check and the mistakes to avoid.

Square knot

1The knot in plain words

In one sentence…

The reef knot ties the two ends of one line flat around a bundle, like reef points around a reefed sail.

What does it do?

It closes the two ends of a line around something: a reefed sail, a sail cover, a bundle. The knot lies flat against it.

When do I use it?

For reef points, sail ties, covers and small bundles, where what's inside presses against the knot and holds it.

How is it made?

Two half knots, the second the mirror of the first: right over left, then left over right.

When not?

Never to join two ropes that will take a load. It can capsize and pull apart. Use a sheet bend for that.

2Knot ID card

Knot family: Binding knot
Difficulty: Beginner
Holds a steady load: Only when tied around something
Unties after load: Usually, but it can jam under heavy strain
Weak point: Spills if used to join ropes
Also called: Square knot

3How to check it

Step-by-step tying is being checked on real rope before we publish it. Until then, use the illustration and the checks below.

Each end lies beside its own standing part, on the same side.
The knot is flat and symmetrical: two small bights locked into each other.
If the ends stick out across the knot at an angle, it's a granny. Untie it and tie it again.

4Key points

1.
Reef knot = a binding knot for reef points, covers and bundles.
2.
Right over left, then left over right.
3.
Ends beside their own standing parts; otherwise it's a granny.
4.
To join two ropes, tie a sheet bend instead.

5Frequent mistakes

Mistake: Tying right over left twice.
Correct: That makes a granny knot, which slips or jams. Mirror the second half: left over right.
Mistake: Using it to join two ropes that will take a load.
Correct: It can capsize and come apart. Join ropes with a sheet bend.
Mistake: Tying it in ropes of different size or in slippery line.
Correct: That's where it is least reliable. Use a bend made for the job.

6Don't mix it up

7Questions sailors ask

What is a reef knot used for?

To tie the two ends of a line around something: reef points on a sail, sail ties and covers, and small bundles.

What is the difference between a reef knot and a granny knot?

In a reef knot the second half knot mirrors the first, so it lies flat. In a granny both halves go the same way, and it slips or jams.

Is a reef knot the same as a square knot?

Yes. Square knot is the usual name in the US and in scouting; sailors call it the reef knot.

Can I use a reef knot to join two ropes?

Not for ropes that will be loaded: it can capsize and pull apart. Use a sheet bend instead.

8Test yourself

Question 1/4

What is a reef knot mainly for?

Test all knots in the knots exam →

Screen study teaches what the knot is for and how to check it. It doesn't prove you can tie it: practise with real rope, and never use these knots for climbing, rescue or anything that holds a person.

Sources

Content reviewed on September 21, 2026