Second base, or 2B, is the second of four stations on a baseball diamond which must be touched in succession by a base runner in order to score a run for that player's team. A second baseman is the baseball player guarding second base. Also called 2B, or second bagger, the second baseman often possesses quick hands and feet, needs the ability to get rid of the ball quickly, and must be able to make the pivot on a double play. Second base is also known as the keystone sack. In the numbering system used to record defensive plays, the second baseman is assigned the number 4.