Chaining or tethering dogs is considered cruel in more and more jurisdictions. Tie-outs have been shown to cause frustration, anxiety, aggression and neurotic behaviors in dogs. Plus, he could injure his neck, get strangled to death, get attacked by other dogs/animals, or even stolen out of your yard. At least use an overhead trolley line with a 15-20 foot chain/cable for the dog's sake. Make sure he has shade and a bowl of clean water at all times.