Just finished installing this at my daughter's house. She has a fenced back yard, but the dog kept digging under it and she was afraid she would have to get rid of her. Since the dog is otherwise very sweet and a wonderful playmate for my 6-year-old granddaughter, I knew we had to do something to keep her. We installed the fence, not in the ground, but on the existing fence a few inches off the ground and looped back some 3 feet above that wire. To begin, I should have set the collar at level 3. Instead, I set it at 5 and gave the poor dog a really rough shock. I set it to 3 and she feels it but doesn't yelp like she's being tortured. At the moment, she is leery of going back outside, but I think she'll be ok as soon as she realizes she still has the rest of the yard to play in.