My house in Ottawa shares a driveway with the house next door. This is pretty standard in the older neighborhoods in Ottawa.
The driveway is a deeded right-of-way. Three feet of the right-of-way is on my property, and five feet is on my neighbor's. It leads to our respective parking spaces at the backs of our houses. It's to remain clear to allow passage of people, vehicles, and animals (it's over 100 years old, so animals actually get a mention in the deed.)
My neighbor has never been happy about this right-of-way, and he's convinced that since he owns the wider 5 foot share, that he calls the shots on use of the driveway. I should note that the neighbor doesn't actually live in his house, it's always rented out.
Well, my house was also rented out for a few years. My neighbor moved back into his for a couple of months in 2007 (he does this periodically, followed by a rent increase for his new tenants), and took a disliking to my tenants.
Now, for all I know, my tenants could have been annoying (I never met them, an agency rented the house for me.). However, he was very upset at the fact that my tenant's kids would play in the driveway. The kids once left a toy wagon in the driveway (I know, because he sent me a photo of it), and I guess that was the final straw. Previous offenses had included toys left in the kid's own back yard (he didn't like the sight of them), and one of the kids asking his adult daughter once if he could borrow their hose to wash his bike.
To try to keep my tenants off "his" turf, he painted this:
It's faded somewhat in the intervening years, but yep, it is what it looks like. It's a "do not cross" line. Right down the property line. Even though the driveway is a right-of-way, and residents of both houses (as well as the utility companies) have the right to use it to access parking and the back yards of their houses.
Want to know what my absentee neighbor does for a living? He's a diplomat with Foreign Affairs.