A framed lattice panel can serve a multitude of functions on a deck. It can screen off the area under the deck platform, serve as the sides of the deck or top the existing sides as a privacy screen add-on.
You can measure and trim premade wooden or vinyl lattice panels to fit the space between the posts and rails of the deck. Then you position the trimmed lattice panel, level it and fasten it to the posts and rails with nails or screws.
Setting posts for a lattice privacy screen correctly requires proper planning, placement and installation of the posts. Since the posts will dictate the outcome of the finished product, each post should be set in its proper location and plumb with additional posts.