Hi! This is Jon on behalf of Expert Village. In this video clip, we will be installing our upper back piece. To keep our bookshelves from falling over once we have books on them, we are going to be installing a board that goes across the upper back and we are going to use this board to be able to screw through it into the wall and that is really going to secure our bookshelves. The first thing we need to do is to install a shelf at the highest possible level. Next we need to take a measurement as to how wide that piece can be and we can actually go up to 1 3/4 but I am going to make mine at 1 1/2. Once we have made our piece, we can go ahead and slip it into place and see how it fits and that looks like it fits pretty good. So we are going to go ahead and glue it and pin nail it and that is going to hold it in there. And I am actually going to be pin nailing it from the back with little bit shorter pin nails.