Cut the lattice screen down to the size appropriate for your deck railing. Mark the measurements onto the wood and use a circular saw to make the cuts.
Cut four pieces of 1-by-4 wood to form a frame that fits around the lattice screen, which gives it a solid base to attach to the deck railing and prevents warping of the wood over time.
Form a rectangle with the frame wood and attach at the corners with a mending plate and corner joint. Use a drill to screw these metal pieces into place.
Turn the completed frame over and place the lattice screen on top. Screw it onto the frame using washers and 1-inch pan-head screws.
Line up the framed lattice screen with the edge of your deck railing. Nail the frame to the deck railing using 2-inch wire nails.