How should a referee signal a valid hit?

A referee signals a valid hit by raising their arm because this is a widely recognized indication of a scored point in fencing. This gesture not only captures the attention of the fencers and spectators but also communicates clearly to everyone involved that a valid scoring action has taken place. Raising the arm is a conventional signal that maintains the flow of the match and avoids interruptions that could arise from using other methods, such as calling names or blowing a whistle.

The other methods, while they may have their place in communication or other sports, do not effectively convey the same clarity in the context of fencing scoring. Using flags or whistles might confuse the participants regarding the status of the match, and calling out names is neither practical nor clear in signifying a valid hit. Therefore, the referee's arm raise is the standard and most efficient method for signaling a valid hit in fencing.