I have a 4' fence around my back yard, which is enough for my 3 fence-respecting dogs, but I want to increase it to 6' by adding something to the top. My desire went way up last night when the neighbors came home with a pitbull. Thrills. I have seen it done various ways, but am looking for suggestions. My current fence is chain link, so I do have a good top beam to wire or tie something to. (BTW, they assure me that the pitbull will always be crated in their basement because they also have cats and don't want the cats disturbed...)