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The sails of a windmill are known in Sussex as "Sweeps", and are carried on the end of the cast iron Windshaft. Cast into the end of this shaft is a Poll End, which is a double box with openings at right angles, each opening being rectangular in cross-section. Each pair of Sweeps is carried on a central wooden beam or "Stock" and this is fixed into the Poll End with wooden wedges.
The rectangular shutters are all operated simultaneously with an iron Striking Rod which passes through the centre of the Windshaft and moves the four-arm Spider which can be seen painted black. This provides the mechanical linkage to each Sweep to open or close the shutters. At the opposite end from the Sweeps the Striking Rod is linked to an iron crank or "Rocking Lever" which is operated using weights hung on a chain, and which is used to balance the force of the prevailing wind to keep the shutters closed. If the wind pressure increases it overcomes the force provided by the weights on the shutters and the open, spilling the wind. This design was an attempt to provide constant speed operation.
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