Question About Golf - Please Help?

I was at the Exelon Invitational Today which is a fourball tournament which includes Paul Casey, Kenny Perry, Anthony Kim, and Jim Furyk. Its a small tournament but it was fun to watch. Anyway, when golfers are hitting their approach shots, form say 50 yards away, and one person puts it 4 feet away, and then the next person hits that ball, what happens? I know if your putting and it hits the ball its a 2 stroke penalty, but if your far away your not going to mark your ball on the green. I know their is probably a simple answer, but can someone clear this up for me. Thanks a lot