[AtlUmpSteve]

And, my note regarding NCAA clarifications in the other thread also applies.

"Within" means completely within; the lines are part of "within", no part of the foot may be out. The batter must be within the batter's box at the time of the pitch.

"On" means any part of the foot is in contact with any part of the line. The batter may be on the line at the time of contact, and is not out.

"Out" means a foot (or other body part), or every part of that body part that is touching, is touching completely outside the line. If the batter's foot (the part that is in contact with the ground) is completely out of the box at the time of contact, the batter is out.