What do athletes have to do at the call room, and what happens if two of their events clash?

Call room: where a Call Room operates for an age group, the athlete must report to it before joining their event. An athlete who does not report (other than for the first field events of the day) is not permitted to compete in that event. The exceptions are an athlete taken to a clashing event by an official, and times when carnival management announces otherwise, such as telling athletes to go straight to the first field event. If heats are condensed or become a straight final, no athlete may join the event once the decision has been announced. Each event gets 2 calls, except at fully timed carnivals.

Clashes: an athlete must never leave an event on their own to go to a clashing one. An Event Clash Manager (when appointed) takes the athlete from one event to the other, and an athlete who leaves without the Clash Manager cannot continue in the event they left. Except in high jump, the Chief Judge may let the athlete compete out of round and out of order, but never two or more consecutive trials. In high jump the athlete may compete out of order and rejoins at the current bar height. An athlete taken from a field event to a track event must return to the field event straight after the track event.