Shackle is one of the most common rigging hardware, is composed of two easily disassembled parts of the body and pin, widely used in electric power, metallurgy, petroleum, machinery, railway, chemical industry, port, mining, construction and other industries. According to the shape of the body, it can be divided into D-shaped shackles and bow shackles. The top of the D-shaped shackle is semicircular, and its inner radius is equal to half of the inner width between the two ring eyes, also known as U-shaped shackle or straight shackle; The buckle top of the bow shackle is more than half round, and its inner radius is greater than half of the inner width between the two ring eyes, also known as the Ω shape shackle or horseshoe shape shackle.