A base on balls (BB), also known as a walk, occurs in baseball when a batter receives four pitches that the umpire calls balls, and is then entitled to reach first base without the possibility of being put out. The base on balls is defined in Section 2.00 of baseball's Official Rules, and further detail is given in 6.08(a). It is considered a faux pas for a professional player to walk to first base; the batter-runner and any advancing runners normally jog on such a play, with Pete Rose earning his nickname "Charlie Hustle" due to him running towards first on a walk.