The Reef Knot

One of the simplest of knots. Once uncommon in climbing circles, it has gained favour in recent years for tying abseil ropes together, though this use has declined since the uptake of the overhand knot.

Attribute	Notes
Strength	45 -50%
Ease of Tying	Possibly the simplest of knots.
Recognisable	Easy to recognise - the knot is symmetrical if tied correctly.
Also known as	Square knot.
Usage	Tying two ropes together.
Advantages	Simple. Easy to undo after loading.
Disadvantages	Tying two ropes of different diameters. Can work loose - best backed up with a double fishermans's knot, which sort of defeats one of the objectives of using such a simple knot. Symmetrical: so has an increased tendency to catch when being pulled after an abseil.