Most people know the rules on changing hands in bowling. In the PBA you can switch hands whenever you want. In USBC certified competition where handicap is involved, you must be right-handed or left-handed corresponding to the hand you established your average with and stick with it once a competition begins. A bowler can be allowed to change hands during an event if they are injured. In scratch tournaments you can use either hand, unless a tournament has a specific rule forbidding it....