Bowline draws tighter as tension is placed on the standing part of the rope. The "Birmingham bowline" has two loops; the working part is passed twice around the standing part (the "rabbit" makes two trips out of the hole and around the tree). Other two-loop bowline knots include the Spanish bowline and the bowline on the bight; these can be tied in the middle of a rope without access to the ends. A triple bowline is used to make three loops. A Cossack knot is a bowline where the running end goes around the loop-start rather than the main part and
Blood knot Blood knot A blood knot (barrel knot) is most usefully employed for joining sections of monofilament nylon line while maintaining a high portion of the line's inherent strength. Other knots used for this purpose can cause a substantial loss of strength. In fly fishing, this serves to build a leader of gradually decreasing diameter with the castable fly line attached at the large diameter end and the fly or hook at the small diameter end. The principal drawback to the blood knot is the dexterity required to tie it. It is also likely to jam, which is not a concern