Airheadeness must be contagious. I went back and reread my posting. It was not what I meant to say. Had an airheaded student in my office when I typed that up. What I meant to say (and guess I might be wrong about this) is that legal guarding position is "forfeited" if the defender is standing under the basket and the post player is going up for the shot in between the defender and the backboard. If I'm not mistaken, I saw this called as a blocking foul once.