I have a gorgeous 24 pound Shiba Inu that was escaping and making us completely crazy.
We did not want to mess with chicken wire, worried it was sharp for us to work with, and worried the dog might mess with it and get cut herself. We have a wood board on board older fence. For the digging under issue, we bought 1 foot square cement blocks at Lowes, they seemed to be the cheapest thing I could find. We laid them along the perimeter of the fence. I know, it is nuts, but I figured they could be removed easily enough (?) by the next house owner. They are heavy enough and large enough to prevent her from moving them, or digging under them and out.
Of course, this led to her chewing and trying to break out THROUGH the fence, instead of under it. The fence is getting old, and weak along the bottom. After replacing some slats and sections, DH came up with another cheap solution. He ripped some exterior plywood into 10-12" boards, stained them, and nailed them horizontally across the bottom of the fence. I know, it sounds and looks a little crazy. It is like a prison yard bunker back there.
SUCCESS!! She has not escaped in a year. I love my Jazzy, and she loves to run free and fast in the backyard. We lost her in nearby woods, she was found on a 45mph road, it was a nightmare. She would not come back to us when called, it was all part of the game for her. We would usually only catch her if strangers joined the pursuit, she would go to them in curiosity.
She is the red one in my icon here. The black one would never follow her, he would cry and whine to sound the alarm that she had escaped. (he is also known as "the good one").