The official rules of high school baseball are established by the National Federation of State High School Associations (NFHS) based in Indianapolis. According to the NFHS website, the association is the preeminent source of official high school baseball rule interpretations.
Obstructing base runners by means separate from fielding a ball in play is considered illegal under NFHS rules. Obstructed runners are awarded at least one base. If a runner is deemed obstructed, play continues until either the completion of the play or until the ball is deemed dead.
Under NFHS rules, bats cannot exceed 36 inches in length or 2 5/8 inches in diameter. All non-wood bats must meet the standards dictated by the "Bat Exit Speed Ratio" or BESR--a scientific performance measure aimed at instituting bat safety.
NFHS rules prohibit the pitcher from wearing a fielding glove whose color will interfere with the batter's vision of the ball. The fielding glove color of other players is not restricted. If a fielder misplays a batted ball, his first priority by rule must be to avoid undue and accidental contact with base runners.
Pitching Rules and Restrictions
NFHS rules allow for two pitching positions: the windup and the set position. The position of the pitcher's hand during the windup can be separate. Managers are required to adhere to the pitching restrictions set forth by the state association for which they play.
Under NFHS rules, substitute pitchers are allowed eight warm up pitches from the mound before the resumption of play. The official rules also dictate that umpire undershirts must be blue if the umpire chooses to wear one. Numbers on each player's uniform must be at least eight inches high. Caps are mandatory.