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Windmills were works of art, and no two mills were alike. Each was individually made rather than mass produced The windmill, which was always referred to a "she" by the miller, usually took the name of the village it served. If not, some descriptive adjective or phrase, as in the case of the side-by-side Jack and Jill mills of Clayton, Sussex, or the miller's name might be used. Although the building of a windmill was carefully planned, until the mill was operating in place, no one could know how effective it would be. Two mills too close together, for example, could set up wind turbulence which would render each ineffective. A windmill was usually built on a mound or a hill to catch the wind but flat areas coudl also be used as long as wind turbulence created by trees, buildings, or other mills could be avoided. Often mounds were built specifically for the placement of a windmill. In addition to grinding, grain, mills served as a power source, but, in areas where there were rivers and streams, water mills took precedence as a power source.

The design and operation of a windmill depended on various characteristics of the wind such as wind speed and changes in wind speed, wind direction and changes in wind direction, wind turbulence, and the height of the wind above the ground. An average windspeed of 15 to 25 miles per hour and a prevailing wind were necessary for operation of a mill. The critical component of a mill's operation was the sails. The force of the wind on the sails caused them to turn and rotate the axle, or windshaft, on which they were set. The brake wheel, located inside the top of the mill, also was attached to the windshaft, and its movement drove the millstones and all other machinery inside the mill.

Mills usually had four sails, but five, six, and eight-sailed mills were also built. The earilest sails were wooden, cloth-covered frames known as common sails. They were light and powerful but had to be stopped for the miller to furl the sails. As windmill design advanced, the cloth sails were replaced with sails with shutters. In 1807, William Cubitt invented a sail which could be adjusted while the sails were turning. The shutters of this sail could be opened and closed automatically and worked like venetian blinds to aid in utilizing the wind. A windmill's sails had to always be square into the "eye of the wind" as the mill was designed and balanced to resist pressure from the front only. If a mill was tail-winded, the cloths or shutters could be blown out, the cap blown off, or the mill itself blown over, often with the miller in it. Because the wind changes, the mill had to be capable of being turned into the wind whatever the direction. This was called "winding the mill." The turning gear was the tail pole, and bodily force was used to effect the turn.

When the mill was closed, the miller was very careful to leave the sails set in the configuration of a St. Andrews cross as this position left the sails balanced and afforded the least amount of strain. The position in which the sails were left could also convey messages to the people of the area. Shutters were removed for mourning--the more shutters removed, the closer the relationship of the deceased. In some areas, lanterns were put on windmills to convey signals to smugglers. The following illustrations show various messages sent by sail positions:

There are records of windmills having been moved. Sometimes this was done to find a better site with more wind. When a mill was sold, the new owners would often change its location as moving a mill was cheaper than building a new one. The post and smock mills were never considered permanent structures because of their wooden construction and thus were often moved. The moving was accomplished by placing rollers under the outer structure after the machinery inside the mill had been removed. Smock mills could simply be taken apart and reassembled at the new location.

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