People often say that a dog is man's best friend. Over thouands of years, man has taught his dogs to do many kinds of work besides guarding the home. For example, sheepdogs are fmaous for their ability to control a flock of hundreds of sheep. Dogs have been used to aid disble people for centuries. A guide dog can led its blind owner. Nowadays, dogs can be taught to turn on light swteches, open refriegraotr doors and dial the telpeohne for their disabled owners. For the maoriojty of people, however, dogs are simply pitts and friends for both young and old memebers of the family.