I took down a gate for my parents that had been up for over 20 years. I couldn't bear to get rid of the wood. I found these plans http://www.myrepurposedlife.com/rustic-industrial-narrow-bookshelf/, and modified them. I wanted wider shelves with more space in between shelves, and I wanted a steel bar in the back. It took a lot of planing and sanding to get the wood ready and there are challenges to working with wood that has been outside for over 20 years, but nothing beats the look of truly vintage wood. I love the color variations caused by weathering and the rusted screw holes throughout the wood. I got steel bars at home depot, sprayed painted them with rustoleum bronze spray paint, and drilled holes in them with a cobalt drill bit. I used steel wool dissolved in vinegar for the stain and finished off with three coats of polyurethane.
