Originally Posted by Tokyorich
Can you do it with an SF card? I don't think they are time stamped.
But the Metrocard will know where you got on, and won't let you out at the same station. One over, yes. Same with the Suica for JR. You can always go to the station office and claim that you got on but something came up and now you have to leave. They would let you out without much questioning.