I am looking for guidance and a list of what I need to build a privacy screen on top of a 600mm sandstone wall. Screen will be 1200mm high and the length L-shaped, 2 x 3600mm. I have seen various aluminium posts etc. online but am not sure what I actually need and the quantities. Not sure if I can find or use 3600mm compositecdecking boards with a gap, maybe 10mm between each. Minimum I guess I need 2 end posts, a corner post (with flanges to bolt to sandstone). Can I screw a c channel onto the posts to slot the decking boards in? If I need to cut t,he 2 lots of 3600mm decking, into 4 x 1800mm lengths I will need 2 more posts and c channel on each side of the new centre posts. I would appreciate some advice here, am 8 on the right track?