To make mills work, millers are needed and their training is extensive. The miller must have an insight in the technique of the mill, in the weather and in all kinds of safety aspects, important for the work and for maintenance. The work of a miller is to make the mill turn to grind, to saw, to pump or to extract oil. The miller manages the speed of the sails of a windmill by spreading sailcloths on them. An optimal position is obtained if the mill is turned with its back to the wind. This is done by the fantail, which can rotate. For a water mill the miller must keep a keen eye on the water wheel that drives the mill, which must turn continually. The level of the water and the flow are important in this process. The type of water wheel allows to distinguish four kinds of water mills. The profession of miller used to be passed on from father to son.