If the manager decides it's time to change the team then this is the signal you'll see on the touchline. The arms go up in the air and holding on to both sides of the flag, it is hung above the head ...

Other match officials (two assistant referees, a fourth official, two additional assistant referees, a reserve assistant referee, a video assistant referee (VAR) and at least one assistant VAR (AVAR)) ...

Law 5: The Referee - powers and duties, Video Assistant Referee (VAR), referee's equipment, referee signals… Law 6: The Other Match Officials - assistant referees, fourth official, assistant ...

Assistant referees are also required to be FIFA listed ... Assistants carry a flag to signal their decisions for fouls, offside or when the ball is out of play. The official in the middle signals ...