When we lived in Texas we had a half German Shepard Dog, half Siberian Husky. The back yard was surrounded by a 4' tall chain link fence. Yup only 4 feet tall. We had a dog house for him and it was 3.5' tall with a flat, slightly sloped roof. He liked laying on the dog house roof. We kept the dog house pushed right up to the fence. The roof of the dog house was a mere 6" from the top of the fence. Can you imagine my surprise when we found him outside the fence? He tunneled under the fence. He would never jump off the dog house to get out, he would dig. I guess that was more challenging.