Yosemite bowline form a highly dangerous slip knot. Additional safety is achieved by tying with a tail (see below). When finished, the working end forms a figure eight. Because of the danger of incorrectly tying the Yosemite bowline, it may be safer and less error-prone to use a standard or double bowline with a backup stopper knot added to the tail, such as a double overhand knot tied around the loop. The Yosemite finish can be applied to other bowline variants, such as the double bowline. While the knot's versatility suggests it as a convenient tie-in for attaching a climbing rope to
Reef knot reef knot must emerge both at the top or both at the bottom, otherwise a thief knot results. Although the reef knot is often seen used for tying two ropes together, it is not recommended for this purpose because of the potential instability of the knot, and over-use has resulted in many deaths (see Misuse as a bend). The reef knot is at least 4,000 years old. The name "reef knot" dates from at least 1794 and originates from its common use to reef sails, that is to tie part of the sail down to decrease its effective surface area