THE DELIVERY OF THE BALL—FAIR AND UNFAIR BALLS.
RULE 30. A Fair Ball is a ball delivered by the Pitcher while standing in his position, and facing the Batsman, the ball so delivered to pass over the Home Base, not lower than the Batsman's knee, nor higher than his shoulder.
RULE 31. An Unfair Ball is a ball delivered by the Pitcher, as in Rule 30, except that the ball does not pass over the Home Base, or does pass over the Home Base above the Batsman's shoulder or below the knee.