In the past, I have used invisible fence and electric fence. My previous dogs got out of both. I think an electric fence used in conjunction with a standard fence is the best method if necessary. I have had dogs that climb or jump the fence and dogs that push under. Bars across the bottom usually mean deeper holes to fill. The dogs can hear the “hum” of the electric fence and know when it is working. I currently have 2 mastiffs in a 5’ chain link fence. I have braided wire across the bottom instead of bars. I have to walk the perimeter about once a week and make repairs. I have considered an electric wire across the bottom to discourage digging under. The most recent escape was through the gate on concrete. The younger mastiff chewed off the wire tying the fence to the frame. I would much rather shock my dog than let him get out in the road and get hit by a car. I would rather cause a little pain/discomfort that have him get poisoned. P.S. My girlfriend routinely uses a Transcutaneous Electrical Nerve Stimulator or TENS unit on me. I kind of like it.