Chequered flag

It is shown to the leader first, at the moment they complete the final lap, and then to every car behind as it crosses the line. A driver's race ends when they take it, which is why a car that stops on the last lap can still be classified if it has covered enough of the distance.

The flag is waved for practice and qualifying too, where it means the session clock has expired. A driver already on a flying lap when it falls is allowed to finish that lap — the rule is that you must have crossed the line before the flag, not that you must be done.