One of the regulars at the bar brought a set of wooden blocks to hang above the stairs that read "Do Not Block The Stairs" as a gift for my coworker who spends at least twenty minutes a night asking people to move off the stairs, which give access to our fire exit.
I hung them across the stairs. A dude walked up to them. Stopped. Read them. Cocked his head. Made eye contact. Asked "Is it cool if I stand here?"