This may look odd but it works brilliantly. Chickens are brilliant at knocking bowls over. They like to stand in them, or on the sides and bowls will easily tip. This little invention is basically a drain-pipe with a strip cut out. It has stoppers at the ends fixed with metal bands. We have found that the chickens soon learn not to stand on it as it rolls and scares them. The slot is big enough for them to drink from but small enough to stop too much evaporation in the summer months. This means less work filling it up!  I would say you could use this as a feeder too but since we don´t give our chickens that much food we just throw it on the floor for them to scratch.