Peter, demarcation is one word that accurately describes the process, I don't disagree with that.

But in the yards there was also another word in common use that got across the message to anyone thinking about it: don't encroach on my trade's patch. Tried synonym in the search terms. All that my google search turned up was restrictive practices, closed shop, none of which were what I was looking for. It will come to me, probably around 3am in about 3 months time, which is about the speed of my memory recall at the moment.