The Five Essential Knots Every Sailor Should Know

There are hundreds of knots and a sailor needs about five. The useful thing to learn about each is not just how to tie it, but where it belongs, what it costs in strength, and how it fails. A knot you cannot predict is a knot you should not use.

1. Bowline — the fixed loop

A loop that will not tighten and will not jam. It retains around sixty to seventy per cent of line strength, which is a real cost, but it can be broken by hand after taking a heavy load, and that convenience is why it is on every boat.

• Use it for: a loop in the end of a line, mooring, a temporary attachment, a rescue line in a drill.
• Strength retention: 60–70 per cent.
• How it fails: not by slipping under load, but by capsizing when slack and shaken. A stopper knot in the tail removes the risk.
• Do not use it in: HMPE line, which is too slippery for the knot to lock.

2. Figure-eight — the strong loop

Symmetrical, strong, and easy to inspect — two parallel strands on one side, a clean pair of loops on the other. Retraced back through itself it makes a loop that retains roughly seventy-five to eighty per cent, better than a bowline.

• Use it for: load-bearing loops, stoppers, anything where someone else will check your work.
• Strength retention: 75–80 per cent as a retraced loop, around 75 per cent as a stopper.
• How it fails: it jams. After a heavy load in stiff or small-diameter line you may not get it undone without cutting it.
• Watch for: an incomplete retrace. It looks almost right and is not right at all.

3. Round turn and two half hitches — the reliable tie-off

The knot to use when you are making a line fast to a post, a ring or a rail and you want it to stay there. The round turn takes the entire load, so the two half hitches only have to hold the knot's position — which is why this knot works reliably where a clove hitch does not.

• Use it for: mooring, attaching to a ring or a bollard, any permanent tie-off.
• Strength retention: around 70 per cent.
• How it fails: it does not, provided the round turn is properly made. Skip the round turn and you have a knot that slips.
• Advantage: it can be tied and untied under load, and it can be adjusted by feeding line through the turns.

4. Clove hitch — the adjustable grip

Two crossing turns around a post. Quick, one-handed, adjustable by sliding along a rail. And only trustworthy when the tension never drops.

• Use it for: fender lines, temporary tie-offs, rail work where the load is constant.
• Strength retention: 60–65 per cent.
• How it fails: the load slackens, the hitch loosens, and it releases. It grips by friction alone.
• Always: back it up with half hitches or a stopper if the load can vary.

5. Sheet bend — joining two lines

The bend that works between lines of different diameters, which a square knot does not. A bight in one line, the other threaded up through it, around behind both parts and tucked under itself.

• Use it for: joining a heavy line to a light one, temporary repairs, messenger lines.
• Strength retention: 55–60 per cent; around 65 per cent doubled.
• How it fails: the two working ends come out on opposite sides, and the bend spills. Both tails must exit on the same side.
• Upgrade it: a double sheet bend for anything slippery, small or heavily loaded.

What every knot costs

The habit that matters more than the knot

Dress and set every knot before you load it. Dressing means arranging the parts so they lie correctly and the load path is clean; setting means loading it once by hand so the knot seats. A knot that is tied correctly but not dressed can be weaker and less predictable than one that is slightly wrong but properly set. Then leave a tail of ten diameters, and load it once while you are watching.