5.07 (a) (1) The Windup Position
The pitcher shall stand facing the batter, his pivot foot in contact with the pitcher’s 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. When a pitcher holds the ball with both hands in front of his body, with his pivot foot in contact with the pitcher’s plate and his other foot free, he will be considered in the Windup Position.
(A) deliver the ball to the batter, or
(B) step and throw to a base in an attempt to pick-off a runner, or
(C) disengage the rubber (if he does he must drop his hand to his sides).
In disengaging the rubber the pitcher must step off with his pivot foot and not his free foot first. He may not go into a set or stretch position—if he does it is a balk.