The double figure eight knot has the disadvantage of weakening the strength. The double figure eight knot has the advantages of strong endurance and firmness. It is very trustworthy in terms of safety and is often used by mountaineers as a life-saving knot. The size of the loop of the double figure eight knot is difficult to adjust, and when the load is overloaded, the knot is pulled too tight, or the rope is exposed to water, it will be difficult to untie and the strength will weaken.