a wagon and the oxen are simply backed over this pole, the pole is then raised between them and a backing bolt is dropped into the chains on the yoke irons in order to haul the wagon. Head yokes are used in southern Europe, much of South America and in Canada. Withers yoke A withers yoke is a yoke that fits just in front of the withers, or the shoulder blades, of the oxen. The yoke is held in position by straps, either alone or with a pair of wooden staves on either side of the ox's withers; the pull is however from the yoke itself, not from the staves. Withers yokes particularly suit zebu cattle, which have high humps on their withers. Withers yokes are widely used in Africa and India, where zebu cattle are common. Comparison Although all three yoke types are effective, each has its advantages and disadvantages. As noted above, withers yokes suit zebu cattle, and head yokes can of course only be used for animals with suitable horns. Head yokes need to be re-shaped frequently to fit the animals' horns as they grow; unlike other types, a single-beam head yoke fixes the heads of the oxen apart, helping them to stand quietly without fighting. A single-beam head yoke may offer better braking ability on downhill grades and appears to be preferred in rugged mountainous areas such as Switzerland, Spain and parts of Italy. Bow yokes need to be the correct size for the animal, and new ones are often made as an animal grows, but they need no adjustment in use. Whichever type is used, various lengths of yoke may be required for different agricultural implements or to adjust to different crop-row spacings. Single yoke A yoke may be used with a single animal. Oxen are normally worked in pairs, but water buffalo in Asian countries are commonly used singly, with the aid of a bow-shaped withers yoke. Use of single bow or withers yokes on oxen is documented from North America, China, Zimbabwe, Tanzania and Switzerland, and several designs of single head or forehead yoke are recorded in Germany. Symbolism The yoke has connotations of subservience and toiling; in some ancient cultures it was traditional to force a vanquished enemy to pass beneath a symbolic yoke of spears or swords. The yoke may be a metaphor for something oppressive or burdensome, such as feudalism,