A watermill is a structure that uses a water wheel or turbine to drive a mechanical process such as flour, lumber or textile production, or metal shaping (rolling, grinding or wire drawing). There are two basic types of watermill, one powered by a vertical waterwheel via a gearing mechanism, and the other equipped with a horizontal waterwheel without such a mechanism. The former type can be further divided, depending on where the water hits the wheel paddles, into undershot, overshot, breastshot and reverse shot waterwheel mills.