The figure eight follow through boating knot is one of the strongest knots. (also can be used for paddling). It is generally rated at 70% - 75% of rope strength. Due to it's strength and the fact that it is easy to visually inspect, it is commonly used by climbers as their "tie-in knot" - the knot that connects the climber to the rope. It forms a secure non-slip loop at the end of a rope. For even greater security, finish the tag end with a backup knot such as one side of the double fisherman's boating knot.