Double bowline with a bight of rope instead of the end. First, learn to tie the bowline by laying the working end on the standing part and twisting to form a loop (the "hole" that the rabbit comes out of). Wrap the loop once more around the working end. Then pass the working end behind the standing part and back down through the double loop. The double bowline is one of the typical tie-in knots used in climbing, along with the figure eight follow through and the Yosemite bowline. The advantage of the double bowline over the figure 8 is that it
Arf invariant of a knot Arf invariant of a knot In the mathematical field of knot theory, the Arf invariant of a knot, named after Cahit Arf, is a knot invariant obtained from a quadratic form associated to a Seifert surface. If "F" is a Seifert surface of a knot, then the homology group H("F", Z/2Z) has a quadratic form whose value is the number of full twists mod 2 in a neighborhood of an imbedded circle representing an element of the homology group. The Arf invariant of this quadratic form is the Arf invariant of the knot. Let formula_1 be a Seifert matrix of