What does the starter's assistant do?

Under World Athletics Competition Rule 23 (and ASA Rule 21.3.6), the starter's assistants:

• check that athletes are in the correct heat or race and that their bibs are worn correctly;
• place each athlete in the correct lane or position, assembling them about 3m behind the start line (or behind each start line in echelon starts), then signal to the starter that all is ready;
• reassemble the athletes if a new start is ordered;
• make sure batons are ready for the first runners in relays;
• once the athletes are ordered to their marks, make sure the crouch and standing start rules are observed;
• after a false start, show the cards: a red and black card to the athlete disqualified, or in combined events a yellow and black card to the athlete responsible and to everyone else in the race for a first false start.