Knots/Binding knots/Constrictor

The Constrictor knot is one of the most effective binding knots. Simple and secure, it is a harsh knot which can be difficult or impossible to untie once tightened. It is made similarly to a clove hitch but with one end passed under the other, forming an overhand knot under a riding turn. The Double constrictor knot is an even more robust variation having two riding turns.

Usage

The Constrictor knot is appropriate for situations where secure temporary or semi-permanent binding is needed. Made with small-stuff it is especially effective, as the binding force is concentrated over a smaller area. Tied over soft material, such as the neck of a bag, use hard stiff cord. Tied over a hard surface, use soft stretchy line. The Constrictor knot's severe bite, which makes it so effective, can damage or disfigure items it is tied around. To exert extreme tension on the knot without injuring the hands fashion handles for the ends using Marlinespike hitches made around two rods.

Constrictor knots can be for used for temporarily binding the fibres of a rope or strand end together while splicing or when cutting to length and before properly whipping the ends. Constrictor knots can also be quite effective as improvised hose clamps or cable ties. Noted master-rigger Brion Toss says of the Constrictor, "To know the knot is to constantly find uses for it...."

Tying

The method shown below is the most basic way to tie the knot. Other methods exist which can be used to tied it in the hand or over the end of the object to be bound.

Make a turn around the object and bring the working end back over the standing part.
Continue around behind the object.
Pass the working end over the standing part and then under the riding turn and standing part, forming an overhand knot under a riding turn.
Be sure the ends emerge between the two turns as shown. Pull firmly on the ends to tighten.

Variations

Double constrictor knot

If a stronger and even more secure knot is required an extra riding turn can be added to the basic knot to form a Double constrictor knot. It is particularly useful when tying the knot with very slippery twine, especially when waxed. Adding more than one extra riding turn does not add to its security and makes the knot more difficult to tighten evenly.

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Make a turn around the object and bring the working end back over the standing part.
Make a second turn following the same path as the first
Pass the working end over the standing part, then under both riding turn and standing part, forming an overhand knot under two riding turns.
Be sure the ends emerge between the turns as shown. The Double constrictor may require more careful dressing to distribute the tension throughout the knot. After working up fairly tight, pull firmly on the ends to finish.

Slipped Constrictor knot

This variation is useful if it is known beforehand that the constrictor will need to be released. Depending on the knotting material and how tightly it is cinched, the slipped form can still be very difficult to release.

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Make a turn around the object and bring the working end back over the standing part.
Continue around behind the object.
Pass a bight under the standing part and riding turn, instead of using the end itself.
Be sure the bight and ends emerge between the two turns as shown. To release, tug on the working end so that the bight passes back through the knot.

Releasing

Cutting the riding turn

A heavily tightened Constrictor knot will likely jam. If the ends are still long enough, it may be possible to untie by pulling one end generally parallel to the bound object and a bit up away from it, and prying it into the opposite end's part to open the knot. The use of a pick, marlinespike, or some other tool able to be forced between parts can help.

If the ends have been trimmed short, or the knot is otherwise hopelessly jammed, it can be easily released by cutting the riding turn with a sharp knife. The knot will spring apart as soon as the riding turn is cut. If care is taken not to cut too deeply, the underlying wraps will protect the bound object from being marred by the knife.

Security

The Constrictor and Double Constrictor are both extremely secure when tied tightly around convex objects with cord scaled for the task at hand. If binding around a not fully convex, or square-edged, object arrange the knot so the overhand knot portion is stretched across a convex portion, or a corner, with the riding turn squarely on top of it. In situations where the object leaves gaps under the knot and there are no corners, it is possible to finish the Constrictor knot off with an additional overhand knot, in the fashion of a Reef knot, to help stabilize it. Those recommendations aside, Constrictor knots do function best on fully convex objects.

If an item, such as a temporarily whipped rope, is going to be cut very close to where a Constrictor binds it a Boa knot may remain more stable.