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
Double bowline is easier to untie after being weighted in a fall, and so is used by sport climbers who take multiple lead falls and then have trouble untying their figure eights. The disadvantages of the double bowline are that it is less secure than a figure eight knot, takes longer to tie, and is not as easy to check. Unlike the figure eight, there are many variations of the bowline, with ambiguous names, and some are not safe for climbing. The Bowline on a bight, when re-threaded instead of being tied on a bight, can also be used for tying into