The easiest solution would be to not let him in the yard without a leash and your supervision. Even if he did stay and not move, let's just say that a squirrel went by and he decided to chase it, or a loose large dog decided that he'd be yummy for lunch. I don't know if you plan on leaveing him alone, but shih tzus are extremely expensive nowadays, and people want them now more than ever. What if someone stole him? People steal dogs all the time. No matter what the situation, I wouldn't take the risk..