Water that flows from rivers and streams is a valuable and plentiful energy resource. People learned to use the power of running water to operate the small mills that were important to their families. Gristmills ground the grain the farmers grew. Sawmills cut their tumber. Carding Mills combed the wool sheared from their sheep. Waterpowered machines cut nails, turned wood for furniture parts, cut shingles, and did other useful tasks.