My sister has reminded me...
Mrs 'you stole my (imaginary) skirting boards' in North Wales...
Also built a 9ft fence out of scrap wood, pallets, doors etc, claiming we were spying on her.
This was on the boundary line between her property and ours though ours was a good two foot lower down than hers, so in fact the existing 4ft fence her side was so high our side we couldn't see her any but....
Even if we had wanted to, on our side this area was a covered lean-to, which we used to store firewood. At the time of moving in it was early summer and we'd used all the wood so the area looked open. By the time she had finished her Great Wall of Crap, we'd cut, split and brought over several tons of firewood which was then stacked in there... providing a solid wall 5ft deep to the top of the lean-to roof - we couldn't have seen her, even a mouse would have struggled! Total waste of her time, which if she'd listened, she'd have realised.
Speaking of great walls... where my dad now lives is a barn conversion, his immediate neighbours lived in what was the farm house (not now, they burned it down a few years ago but thats another story).
The two properties were split by a boundary wall belonging to them, that took a dead straight line from a pigsty one side to the cowshed the other, and ran for some 40ft
Between buying the property and moving in, we went on holiday.
When we came back, the wall had mysteriously moved 6ft into our side, but dog legged back to theirs at the cowshed end and pigsty end or it would have blocked the cowshed window and pigsty door!
They tried to pretend it had always been like that but.... the cowshed window couldn't open, you could SEE the line of the old wall on the ground their side where they had just taken it down to ground level, and the the mortar was still wet!
Two days of arguing ensued then my dad got somewhat pissed and using a borrowed a small hefty dumper truck, pushed the wall over back into their side, they hadn't even put in foundations, so it all just toppled over.
They were not happy, but seemingly decided they had met their match and rebuilt it where it originally was and never spoke to us again!