Lattice toppers installed to an existing fence not only add decorative detail, but raise the overall height and increase privacy and security. Wooden lattice sheets are available in 8-foot-wide sheets with diagonal or square patterns, allowing you to choose the one that meets your preference. You must extend the height of the fence posts and attach the lattice panels to them. Although you can attach the panels directly between the posts, encasing them in wooden frames gives the fence a finished look.
Determine the desired height of the privacy lattice along the existing fence so you can cut the extension posts to the desired size using a handsaw. Attach a pair of metal tie plates to the lower ends of each extension post using four to six 1 1/4-inch screws. Make sure you attach the plates on opposite sides of a post so the lower, protruding ends are parallel.
Stand an extension post over the top of a fence post so the protruding ends of the metal plates extend over it. Insert four to six 1 1/4-inch screws through the holes in the lower end of the metal plate to join them together. Repeat the process of joining the remaining post extensions to the tops of the fence posts, thereby raising the height of the fence.
Lay a privacy lattice sheet on a level table and cut it to the desired width and height using a table saw. Measure the width and length of the lattice panel and cut four lengths of 2-by-2-inch lumber to form vertical and horizontal frames. Bevel-cut the edges of the framing lumber at 45 degrees using a miter saw so the corners of the frames meet at the angled edges.
Using a router table and router bit, cut a groove along one side of each framing lumber. Press the wood tight against the table so it forms an even groove. Sand the edges of each 2-by-2-inch framing lumber with a 5-inch orbital sander to remove splinters caused by the routing bit, and clean the saw marks.
Insert the long edge of the lattice into the groove along a long 2-by-2-inch lumber to frame it. Grasp the lattice with one hand, and push it into the groove with the other hand so it fits snugly inside. Repeat the process for framing the second long side of the lattice and then the two short sides. The beveled edges of the frames meet to form 90-degree corners.
Drill a pilot hole through the short board and two through the long boards at each corner of the framed lattice panel. Insert 2-inch deck screws through the holes to join the frame to the lattice.
Enlist a helper to hold the framed lattice panel between two post extensions while you check and adjust its level. Insert a row of 3-inch screws along the sides of the panel to secure it to the post below.