The structure and function of universal joints are a bit like joints on human limbs, which allow the angle between connected parts to vary within a certain range. A universal joint is a positive, mechanical connection between rotating shafts, which are usually not parallel, but intersecting. Universal joints are used to transmit motion and power. Single universal joint consists of two yokes, one on each shaft, connected by a cross-shaped intermediate member called the spider. The angle between the two shafts is called the operating angle.