This person's identity is not fixed, usually the student designated by the commander or teacher as the target of action, that is, the "benchmark student." When the commander gives the password of "keep in line with the middle based on xxx", everyone in the queue will turn their heads 45 degrees towards people, and then aim at the line with the corner of their eyes to keep the queue neat.
This kind of training can help students and teams to establish a sense of overall coordination and cooperation, and improve teamwork and discipline.