The Bowline on a Bight is a knot which makes a pair of fixed-size loops in the middle of a rope. Its advantage is that it is reasonably easy to untie after being exposed to a strain. This knot can replace the figure-eight knot when tying into a climbing harness. However, it is critical to use a strong backup knot with plenty of tail beyond the knot.
Varning! Testing shows that the knot might slip when only one loop is loaded. Cavers and canyoneers ought to fasten their cow-tail carabiner through both loops. European cavers widely advocate the use of a figure eight twisted version of the Bowline on a bight.