I mounted the rails with 2" finish nails and a bead of glue along the back. I also put a single 2 1/2" screw in the center to make sure it never pulls away from the wall.
This picture is taken from the stair landing below the rails.
I waited to add the support blocks on the ends until after the rails were in place. This way they can be mounted tight to the wall with glue to give a clean look.
I put the final coat of finish on the front pieces of the shelves, so I can attach them in the next couple of days. After all the big projects we have done recently, its nice to have something small that shows results in just a few days.