The constrictor knot is one of the most effective binding knots. Simple and secure, it is a harsh knot that 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 that features two riding turns.
How to make a Constrictor Knot
The constrictor knot is appropriate for situations where secure temporary or semi-permanent binding is needed.
When tying over soft material such as the neck of a bag, take care to keep the wraps of the knot together. The constrictor knot can damage or disfigure items it is tied around.
To exert extreme tension on the knot without injuring the hands, one can fashion handles using marlinespike hitches made around two rods .
Constrictor knots can be used for temporarily binding the fibres of a rope (or strand ends) together while splicing, or when cutting to length and before properly whipping the ends.
The knot has also been recommended as a surgical knot for ligatures in human and veterinary surgery, where it has been shown to be far superior to any of the knots commonly used for ligation.