The hook is either of a circular section or trapezoidal. The former is meant for light loads up to 5 tons. Shackles according to the difference in shapes are known respectively as D and Bow shackles.

The pins are usually of circular section. The methods of securing shackle pins in positions vary according to the nature of the use of the shackles. When there is a risk of the pin coming out, pins are secured by means of a nut and a cotter pin. A cotter pin affords more rigidity than a plain pin.