I recently built side fences for a stake body bed on a truck from TREX decking and found that it cuts and machines much like wood. The truck will live outside for much of it's remaining life, so I wanted to use a material that would last in the weather. Being that the truck is very small and the decking boards very heavy, I opted to plane them down from 1 1/4" nominal thickness to 3/4" for the fence boards. I also used the TREX material for the posts, but only planned them down to 1" thick. See the photos attached. This material has worked out very well for this purpose and should last a very long time.
Central North Carolina