what are the small pieces of wood on top of the stumps called

The small pieces of wood on top of the stumps are called bails). They are used in the sport of cricket to determine when the wicket is broken or put down. Each bail is made of a single cylindrically shaped piece of wood which has two smaller cylinders of wood protruding from each end. The large central cylinder is called the barrel and the smaller protrusions are the spigots. The spigots are of unequal length: the longer rests alone on one stump, while the shorter rests on the middle stump together with the short spigot of the other bail).