The subway poles are not lounge chairs, especially during rush hour. If there are no seats, multiple hands are meant to grasp the metal rod, lest everyone start falling and flailing. If someone's back has taken over the entirety of it, the move is to dig your fingers around it anyway, hardening your knuckles so that the perpetrator is suddenly struck with an uncomfortable sensation in their spine. They'll get the point.
[Photo via @nycsubhumans]