In the Middle Ages, mustard was a domestic affair, and the inventories of kitchens revealed, among the utensils, mustard mills with which the mustard seeds (Brassica or Sinapis genus) were crushed in vinegar to season dishes. Stone millstones looking like portable mills consisting of two 11,8 inches (30 cm) in diameter millstones - a convex one that did not move, the recumbent or dormant millstone; the other concave that rotated, the rotating or flying millstone – dug with small furrows ejected the product. A wooden gutter allowed the mustard to run off and be collected in a pot (photo). A wheel dresser regularly reformed the furrows using a bush hammer and a hammer.