In our old barn, we had the boards nailed on horizontally on the outside of the stall. When we built our new barn, we decided to nail them on vertically on the inside of the stall. Either way, the boards have been standing up to general wear and tear that happens. I personally like the vertical look. In your case, I sense you're wanting them on the outside of the stall and I think that should work fine (we're proof of that) but if you want to be a little more secure, you could use screws instead of nails to hold the boards in place. Good luck with your project.