We have actually been really lucky in this regard. Our backyard is enclosed by a picket fence reinforced with chicken wire around the bottom. It was here when we moved in last year. Cyrus has never tried to dig or climb out of the fence at all. We are actually hoping to replace our fencing with vinyl this year, so it will be even more secure. Cyrus does not have access to the outdoors when we are not home, however. He is too clever for his own good, and we worry about what he would do if left to his own devices!