Thanks for the ideas!
Isadora is right--he will be on a leash with a pulley, running the length of it.
We cannot attach it to the house. The porch columns aren't strong enough. I wish we could :/
We are making a dog run for our new German Shepherd pup. A 150 ft steel cable will stretch from the front corner of our house back past the run, almost to the woods. We have to sink a telephone pole in front of our house to do this. Does anyone have any ideas on how to make the pole visually...