skateboard grinding

I am making a skateboarding game, and i was wondering if anyone had any solid way of making a guy grind on a rail, specifically constraining the board to the rail. Also if blengines around i was just wondering if you still had a file sitting around. You had like some sort of skatepark and you had a working grinding system, and the link gives me a 404 and the thread is closed, so i was wondering if you had it.