Bowline

The bowline is an ancient and fundamental knot used to create a fixed loop at the end of a rope. A fixed loop is a circle of rope that maintains its size even when tension is applied. Because of its incredible utility, many experts refer to it as the "king of knots." It belongs to a small group of essential knots that includes the sheet bend and the clove hitch.

The bowline is prized because it is simple to tie and remains easy to untie. This is a critical feature because the knot can be undone even after it has been subjected to a heavy load.

To understand how the knot works, you can follow a common mnemonic involving a rabbit. First, you create a loop in the standing part of the rope to serve as a rabbit hole. The working end, also called the tail, acts as the rabbit. The rabbit comes up through the hole, travels around the standing part—which represents a tree—and then dives back down into the hole.

When the standing part of the line is pulled, the knot tightens around itself. If a beginner creates the initial loop backward, they will instead produce an Eskimo bowline. This variation has a more symmetric, triangular shape and is also a stable knot.

While the bowline is generally reliable, it does have specific technical deficiencies. The knot has a tendency to work loose if it is not under a constant load or if it faces cyclic loading. It can also slip if it is pulled sideways. In some circumstances, the bight, or the curved part of the loop, may capsize. To prevent these issues in safety-critical applications, sailors and climbers often use more secure variations. They might also secure the knot by adding an overhand knot as a backup.

The history of the bowline is deeply tied to the Age of Sail. On square-rigged ships, a bowline was a specific type of rope used to control sails. This rope held the edge of a square sail toward the bow of the ship and into the wind. This action prevented the sail from being taken aback by the wind. A ship was said to be on a "taut bowline" when these lines were pulled as tight as possible to sail close-hauled.

Written records of the knot appear as early as 1627. In his work "A Sea Grammar," John Smith referred to it as the "Boling knot." Smith noted its extreme security, claiming that the fastenings would cause sails to split before the knot would slip. Even older evidence exists from the 26th century B.C. During an excavation in 1954, researchers found rigging on the solar ship of the Ancient Egyptian Pharaoh Khufu that suggested the knot's use in antiquity.

Today, the bowline is used across many professional fields with specific requirements. In sailing, it is used to fasten a halyard to the head of a sail or to tie a jib sheet to a clew. It is also a vital rescue knot because it can be tied using only one hand. This allows a person to secure the loop around their waist while holding onto a ledge or a hole with their other hand.

The Federal Aviation Administration recommends the knot for securing light aircraft. When tied, a rope retains approximately two-thirds of its original strength. In the United Kingdom, the knot is a required part of the Qualified Firefighter Assessment.

Many specialized variations of the bowline exist to handle different environments. The Yosemite bowline is a common choice for climbers. For wet conditions, the water bowline is used because it is more resistant to jamming. The round turn bowline adds an extra turn to the "rabbit hole" for more security. Other versions include the Spanish bowline and the bowline on a bight, which can be tied in the middle of a rope without needing the ends.

These variations ensure that the basic principle of the fixed loop can be adapted to almost any mechanical challenge.