<human>: Can you condense the text into three sentences or less?

My parents and I have a three and 1/2 year old yellow English Lab (Louis). He's around 85 lbs(around 38 kilos) and is the sweetest thing. When he was a puppy, we kept him inside until he became big enough that my mother insisted we have a pen built for him in our backyard. We already have another dog who is allowed to sleep inside because she is the most well-behaved dog (and is also a daddy's girl). So, ever since we built Louis his pen, he became an outside dog. Which meant we had to keep him on a long, flexible chain/leash (around 30 ft. or so). We would love to let him off the leash, but anytime we do, he immediately takes off running right out of our yard and down the street. He always comes back but we've had too many other dogs hit by cars that we almost always keep him leashed. We've tried to teach him to stay but it didn't work. We also had a professional trainer come in but that also fell through. Any advice would be greatly appreciated.
<bot>: Our dog runs out of our yard anytime we let him off his chain. How can we successfully keep him in the yard so that he doesn't have to be on a chain?****