Installed along top of hollow vinyl fencing to keep dog from going over the top. 3/4 inch electric conduit inside of 1.25 inch PVC. Four L brackets secured into 2x4 sections cut and placed into the top of the posts. The wood is drilled into vinyl inside the top of post with 4 inch wood screws and the L bracket is attached to the wood. Brackets are bolted together and the upside down L bracket is what goes inside of and holds the metal pipe. The PVC then rolls around the pipe. It will be easy to remove if no longer needed and fence cap can be replaced with no visible holes in vinyl.