For our pergolas we use Laminated Posts. These posts are made by gluing four 2x6’s together. This is a much stronger method than a single 6x6, which have a tendency to warp or twist over time. Sandwiching the 2x6’s together with a glue that creates a bond stronger than the wood itself. This makes a solid piece that will stay straight and strong for decades. Posts are then sanded and the corners rounded so the finished posts measure 5½" square.