You need to show the tickets to get into the exam room and to get your seat. During the exam, the ticket is face up on the table, so that proctors know who you are (I assume). At the end of the exam, tickets were collected. And yeah, I heard the story about someone getting a letter about having something written on the ticket. I guess someone once used the back of the ticket as a cheat sheet, so now everyone is given the evil eye.