When the shuttle falls on the line. It is considered in. Of course more of the debate is WHETHER the shuttle fell on the line or not =p. Only a very small portion of the head of the cork actually contacts the ground because of it's spherical shape, hence why it's so hard to tell.
This was posted below already: http://www.badmintoncentral.com/forums/showthread.php/104941-Defining-IN-or-OUT Even grazing the line is still in. I posted this on the other thread, but you can use this to help you out: http://www.lifesci.sussex.ac.uk/home/George_Mather/TennisCall.html
