Double sheet bend

The bight in the thicker or stiffer rope stays almost straight and forms a kind of fixed frame. The thinner, more flexible rope runs through the bight, around both legs and is then pinched under itself. Under load the bight presses on this nip and holds the thin rope.

In the double sheet bend this turn is made a second time. This gives two nips one after the other, and it becomes much less likely that the thin rope slips through. Because the knot still does not jam badly, it usually unties well after use if you push the bight forward a little.

First: the bight is in the thicker rope. If it is the other way round, the knot slips more easily. Second: the thin rope makes two complete turns around both legs of the bight, and each is pinched under the thin rope itself, not under the bight. Third: the two short tails lie on the same side of the knot. If they lie on opposite sides, that is a weaker form that comes undone more easily.

Dress the two turns so they lie side by side without crossing. Then first pull the thin rope snug at the turns and afterwards pull on both standing parts. Both tails should stick out clearly. A short tug on both ropes shows whether anything moves.

The double sheet bend is the first choice when two ropes of different thickness must be joined, for example a leftover piece of paracord and a thicker rope. It also suits slick synthetic ropes in which the single sheet bend may slip. And it works when one side already has a fixed eye, or when you want to tie a rope to the corner of a tarp – then the eye or the corner takes the role of the bight.

With a very large difference in thickness even this can slip; test it carefully and choose another join if needed. On lines that flap unloaded for a long time it can loosen. For two ropes of equal thickness that must be untied later, there are alternatives such as the Zeppelin bend.

Typical mistakes are a bight in the thinner instead of the thicker rope, tails on opposite sides and a second turn that is not tucked under the thin rope. Each of these makes the knot less reliable. Check joins in guylines or washing lines now and then after wind.

Joining knots often sit exactly where forces are concentrated. So do not hang anything where it could fall on people if the join comes apart. The double sheet bend is a knot for gear. Life-safety use of knots only after proper training with certified equipment.

The name comes from seamanship: the sheet is the line used to work a sail, and the sheet bend was used, among other things, to attach the sheet to the sail. Because it is very old and widespread, it is also known by names such as the weaver's knot – weavers are said to have used it to join broken threads.

To practise, take two ropes of clearly different thickness. Tie first the single and then the double sheet bend and pull hard. Repeat with slick cord. This lets you feel when the second turn makes the difference.