Build the Trellis Frame
Cut two pressure-treated 4x4 posts to the desired height, including the part of the posts that will go in the ground. Cut two 2x4s to the width of the trellis grid. Lay out the posts and 2x4s to form a box, with the 2x4s on edge about six inches from the top of the posts. Assemble the frame with screws. Be sure to measure and line up the posts and 2x4s carefully to keep the trellis from coming out crooked. Leave six inches above the 2x4 at the top of the posts for post caps. Use rust-proof screws and nails for all parts of this project.