A proper chain set-up like Underdog described is the best method of containment for your dog.
x2
Got some pretty serious bulldogs, some of them weight pullers, and I've had them on chain set-ups for a few years. NEVER, ever, had one break off the chain. It's also important to use proper hardware for your set-ups, as well as check the hardware periodically for ware and replace as needed, as well as the chain itself. If a cold shut or o-ring or something rusts up real bad, it is possible that it can break, thus leading to a loose dog and possibly a yard accident of sorts. We personally use metal poles we get from Home Depot, about 10-12ft tall as our 'stake,' We make a hole about 4ft deep, stick the pole down in there, and throw about two bags of quick dry cement and we're good to go.
