Rules can be complicated and confusing. We've narrowed it down to the top 11 that will help you know about the game without being overwhelmed. Every participant in a USBC-certified league must purchase USBC membership. A legal delivery is made when the ball leaves the bowler's possession and crosses the foul line into playing territory. A foul occurs when a part of the player's body encroaches on or goes beyond the foul line and touches any part of the lane, equipment or building during a delivery. The resulting pinfall does not count when a ball leaves the lane before reaching the pins. If the ball comes out of the gutter and knocks down pins, they DO NOT count. If one person bowls on the wrong lane, a dead ball is called and the player is required to re-bowl on the correct lane. If a bowler is not present, their score is their average less 10 pins unless league rules state otherwise. Two lanes adjoining each other shall be used in each game of league. You cannot alter the surface of the ball during competition, only before or after. If a person arrives late, the player may start bowling with frame being bowled unless league rules state otherwise. If a bowler does not complete a game for reasons other than injury, disability or emergency, they receive zero for each frame missed in the game. If a bowler is going to withdraw they must give a two-week notice to both the team captain and league secretary.