When I built the hoarding backs for Flockburgh, I had the devil's own job finding out what these things looked like. Eventually, I made a best guess based on some Edward Beal books and the results look passable.
Time moved on and modern hoardings don't involve so much woodwork. This can be seen on the left with one that has lost it's front. It should look like the one on the right.
I hope this helps somebody one day.