Laminated simply means glued together or glued onto. We use Kiln Dried Pressure Treated Southern Yellow Pine, which is already stronger and less likely to warp than your regular lumber. We sandwich 3 pieces (two 2x4's and a 1x4) together with a glue that creates a bond stronger than the wood itself, then put some screws in there for good measure! This makes a solid piece that will stay straight and strong for decades. Posts are sanded and the corners rounded so they measure just 3 1/2" square.