Stain the trellis a color of your choice. We used Olympic solid-color stain, white #23007, following the manufacturer’s instructions. This project requires only crosscuts of standard dimensional lumber using a table saw or miter saw. To ensure identical lengths of multiple parts for a square assembly, use an auxiliary fence and a stop block on your saw. Select the clearest (least knotted) and straightest boards you can find. This provides the best appearance and easiest assembly.
Pressure-treated lumber is likely to have high moisture content when you buy it. If your boards feel wet and heavy, set them aside for a week or longer to dry out. Stack (sticker) the boards with spacers to allow air circulation, and keep the boards in a dry place out of direct sunlight, such as your garage or shop. If you cut wet lumber and assemble a project with it, the parts are likely to warp or crack around fasteners (which restrict the wood movement) as the wood dries.
The trellis is held in place (sandwiched) between a pair of horizontal mounting cleats (C) at the top and bottom. The inner pair of cleats attach to your porch ceiling and floor using screws in pocket holes. You’ll need a simple pocket-hole jig to drill these holes. The outer pair of cleats attach to the trellis and inner cleats with deck screws.
Although we designed the 83-inch-high x 96-inch-wide trellis to fit the opening on our featured porch, you easily can size it to suit your space. To do this, measure your opening. Then, cut the lengths of the uprights (A) to your measured height and the lengths of the horizontal supports (B) and horizontal mounting cleats (C) to your measured width. When changing the lengths of these parts, you’ll also need to adjust the spacing of the inner parts A and B and the decorative horizontal and vertical rails and stiles -- parts D, E, and F -- as needed to maintain approximate equal spacing. Depending on the overall change in the frame size, you may want to add or omit a rail or stile as well as to adjust their lengths to keep the ends of the parts approximately centered on the widths of the frame members.