The guy sitting next to the empty seat was a stranger to me, unlike the four guys sitting next to him.
I asked the guy if I could sit in the chair next to him. Before he could answer the bartender already had my drink in front of the chair.
He said, "That's my crutch," as he pointed at a crutch next to me leaning against the wall.
I pointed at my pint glass and said, "This is my crutch."
It would have been a more cleaver statement if there was something other than ginger ale in the glass.