There is an international rule requiring all members of the crew to wear the same headgear and uniform. Flags are the referees' way to signal crews. Red means stop and is used to start the race. White flags signal a fair race and direct a crew headed for trouble. Lightweight events indicate the weight of the rower, not the boat.
All rowers weigh in each day they race.
The window of opportunity for weigh ins is not more than two hours and not less than one hour before their first race of the day. FISA allows only amateur rowers to compete in its events. Substitutions in crews are allowed up to one hour before the first heat. However, no more than 50 percent of the crew can be changed from the official entry. If someone becomes injured or ill, he or she can be replaced, yet can return to the crew later at a world championship.