The Windup Position

The pitcher shall stand facing the batter, his entire pivot foot on, or in front of and touching and not off the end of the pitchers plate, and the other foot free. From this position any natural movement associated with his delivery of the ball to the batter commits him to the pitch without interruption or alteration. He shall not raise either foot from the ground, except that in his actual delivery of the ball to the batter, he may take one step backward, and one step forward with his free foot.