Studio One-Off Architecture & Design Not really a fence, and custom built -- the rear wall of the porch is a concrete wall, to which are applied 2x4 vertical nailers, and the horizontal slats are made from 3/4" thick mahogany. But we have added a fence that matches just outside the porch -- we set standard steel posts in concrete, attached 2x6 horizontals at top & bottom, then added 2x4 verticals and then the slats. Careful carpentry -- level, square and equally spaced is the trick. We use Tung Oil on the slats.