When a pitcher pitches the kickball to home plate to the catcher, the pitch will be called as either a strike or a ball by the Head Referee. It's all determined by an imaginary zone on at home plate called the strike zone.
The Strike Zone
The strike zone is an imaginary 3D zone extending 1ft in all directions of home plate. It is used to by the Head Referee to determine if a pitch is a ball or a strike. It is up to the Head Referee to create a mental picture of the strike zone in his mind when calling a pitch.
The strike zone is considered a kickable area; that is, pitches that are within the strike zone are considered pitches that the kicker can realistically hit. This is important to note because it defines the strike zone's purpose. If the kicker does not hit a pitch that can be realistically hit/is in the strike zone, he is punished with a strike (which can later lead to an out). If the pitcher throws a pitch that cannot be reasonably hit/is outside the strike zone, the batter is awarded with a ball (which can later lead to a walk). We will learn more about balls and walks later in this chapter.
The Head Referee's Role
The Head Referee, located on home plate, ultimately makes that decision though. He stands behind the catcher and tracks the path of the pitch as it travels from the pitcher's mound to the catcher. If he sees that the pitch was inside the strike zone, he will call it a strike. If he sees that the pitch was outside the strike zone, he will call it a ball.
Human Error When Calling Strikes And Balls
However, referees are human and humans are not perfect. Fans, players, and coaches become upset if they feel that an umpire has wrongly called a pitch or has an atypical strike zone. While ideally an umpire's call is correct every time, a pitch that is inside or outside the strike zone will not always be called as such. Human error of the umpires is an important aspect of baseball, and it affects many areas of the game -- including the strike zone.
When the Strike Zone Is/Is Not Used
In some situations, the strike zone is disregarded and a strike is called because of something else. The strike zone is only used when the kicker does not kick at the pitch. Not kicking at the pitch means that the kicker did not move his foot as the pitch went by, or that the kicker performed a check kick. Check kicking is when the kicker begins his kick, but his leg does not cross home plate. Check kicking counts as not kicking at all, and the strike zone is still used to determine whether the pitch is a ball or a strike. Referees at first base and third base can help the home plate referee decide if the pitch was a check kick, so the home plate referee can use the strike zone accordingly.
If the kicker does kick, the strike zone is not used and the outcome of the pitch/play is determined by the outcome of the kick. In the next chapter, we will learn more about how strikes are called without using the strike zone.