Which knot is NOT commonly used for safety in rope applications?

The half hitch is not commonly used as a standalone knot for safety in rope applications. While the half hitch can be useful in securing objects or temporarily attaching one rope to another, it lacks the security and reliability required for critical safety applications. When not used in conjunction with other knots, a half hitch can slip under load, making it an unreliable choice for situations where safety is paramount.

In contrast, the double fisherman's knot, figure 8 knot, and bowline knot are well-regarded for their safety and strength. The double fisherman's knot is often used in climbing and rescue applications to connect two ropes securely. The figure 8 knot serves as a strong and reliable knot that can be used to create a loop at the end of a rope, often used for harness connections to climbing and rescue systems. The bowline knot creates a fixed loop that does not slip and can easily be untied after loading, making it a favorite for securing ropes in various applications where safety is crucial.