The great escape dog! We had a dog like that; he was a little cairn terrier. We build a dog-kennel for him in the yard, and couldn't figure out how he escaped all the time. One day we pretended we were leaving and then watched him from the bedroom window. He actually went to the corner of his kennel and climbed up the chainlink fence like a monkey does until he was over the top and then he jumped down. I think once they have made up their mind there is no stopping them.