If you want an existing garden fence to be a little taller, and you don't want to tear the whole thing down and start all over, have no fear. If you used wooden stakes to build the fence, it is possible to make it higher without having to start all over.
Determine out how much more height you want to add to the fence, then drive your stakes deeper into the ground by half that length. For example, say you currently have a 3-foot fence with 4 1/2-foot stakes that are dug in 1 1/2 feet. If you want to add another 3 feet to the fence so that you end up with a 6-foot fence, drive the stakes into the fence another 1 1/2 feet to end up with a total of 3 feet in the ground.
Cut wooden posts to the size needed for the addition on the fence. If you currently have a 3-foot fence, each stake is already 4 1/2 feet long; if you want to make your 3-foot fence into a 6-foot fence, you'll need stakes that are a total of 9 feet long, so cut 4 1/2-foot posts to attach to the top of your stakes. Use a table saw to cut the posts and use the same kind of wood you used for your stakes in the first place.
Attach tie plates to one end of each of the wooden posts. Drill at least three ½-inch screws into the tie plate and wooden post.
Place the wooden posts on top of each stake and attach the tie plates onto the top of the stakes the same way you attached them to the wooden posts.
Wrap chicken wire around the top part of the fence, along the new wooden posts. Use staples to attach the wire to the posts.