Black Rock Mill operated with a water wheel turned by water falling onto it from above. The rotating wheel powered a millstone with a moving top stone and a fixed bottom stone, both cut with grooves that crossed like scissor blades as the top stone turned, cracking wheat and extracting the germ. Hoists and belts, also driven by the water wheel, fed raw grain to the millstones. Flour collected below the stones, was lifted to the top of the mill for drying, and was then packed for shipment. The wheel also powered a massive woodcutting saw, with a cradle feeding logs into the saw to be cut into boards.