Mastering the Reef Knot: Tying it Correctly for Sailing

In a Nutshell...

The reef knot, or square knot, is a simple and versatile binding knot. When tied correctly, it's used to securely join two lines of equal diameter, particularly for reefing a sail or bundling lines. It is not to be used as a bend for joining two active lines under load, as it can slip dangerously. The key to a proper reef knot is ensuring the two bitter ends lie on the same side of the standing parts after the second overhand knot is tied. A common mistake is tying a granny knot, which is prone to failure and occurs when the second overhand knot is tied in the opposite direction.

As sailors, we're taught a handful of essential knots early on, and the reef knot is undoubtedly one of them. While seemingly simple, it's a knot that's often tied incorrectly, with potentially serious consequences. 

This article will guide you through the correct method for tying a reef knot, explain its proper applications on board, and, perhaps most importantly, teach you how to spot a common and dangerous mistake.

What is a Reef Knot & Why is it Called a Square Knot?

The reef knot is a binding knot used to join two ropes of equal diameter. It is also known as a square knot because when tied correctly, the two loops form a symmetrical, square-like shape. This symmetry is your visual cue that the knot is sound. The name 'reef knot' comes from its traditional use for reefing a sail—the act of shortening a sail's area in strong winds. Sailors use reef points (short ropes or cringles) to secure the bunched-up sail to the boom, and the reef knot is the perfect knot for the job because it's secure but relatively easy to untie, even after being under tension.

Reef Knot vs. Granny Knot: A Dangerous Mistake
Tying the Perfect Reef Knot

This is where a little bit of sailing know-how can make a world of difference. The granny knot is a common error and is fundamentally a reef knot tied incorrectly. While it may look similar, it's asymmetrical and unstable, making it highly susceptible to slipping and coming undone, especially when wet or under load.

How to Spot the Difference:

Reef Knot: The bitter ends (the working ends of the line) will exit the knot on the same side as their corresponding standing parts (the parts of the line not being worked).

Granny Knot: The bitter ends and standing parts are on opposite sides, creating a lopsided, unstable shape.

An easy way to remember the correct method is: "Right over left, left over right."

Tying the Perfect Reef Knot

Here's the step-by-step process for tying a correct reef knot:

Stage 1

Remember the mnemonic?

Left over Right and Under;

Stage 2

Right over Left...

Stage 3

...and Under.

Stage 4

Cinch it up tight and you have your finished Reef Knot.

Onboard Applications & When NOT to Use It

A reef knot is a great tool for the following tasks:

• Reefing a Sail: As the name suggests, it's ideal for tying reef points together to reduce a sail's area.

• Bundling Lines or Gear: It's perfect for securing a bundle of coiled rope or other loose items.

• Medical & First Aid: It can be used for tying off bandages or slings in a pinch (though specific knots are often preferred).

Crucially, a reef knot should NEVER be used to join two lines that will be under load. If you're joining two active lines, use a bend like the sheet bend, or a double fisherman's knot for more permanent applications. A reef knot is a binding knot, not a bend. Using it as a bend is a rookie mistake that can lead to a line parting at a critical moment.

In-depth Analysis & Unique Insights

One unique insight I've found in my years of sailing is the 'square knot under load' phenomenon. Sailors often assume a reef knot is a safe bend because it seems to hold well under light tension. However, the true test comes when the line is shock-loaded or repeatedly stressed. Unlike a sheet bend, which cinches tighter under load, the reef knot's structure is prone to a specific type of failure where the bitter ends can slip and the entire knot unravels in seconds. This is why it's a fundamental safety rule to use the right knot for the right job, every time.

For a complete overview of knots and splicing, including their history and uses, return to our main article: A Sailor's Guide to Essential Knots & Splicing.

By Dick McClary, RYA Yachtmaster Offshore & member of the Yachting Journalists Association (YJA)

Frequently Asked Questions (FAQs)

Sources

• https://www.animatedknots.com/reef-knot-square-knot
• https://en.wikipedia.org/wiki/Reef_knot
• https://www.rya.org.uk/knowledge-advice/boating-skills/knot-tying-guide

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