Black

This is a startline only flag. It is shown to all competitors together with the number of the driver for whom it is intended.

This is it. You have probably been very naughty. No joking here this is serious.

The Blue Book Says: The driver must report to his pit within one lap of receiving the signal and report to the Clerk of the Course. A penalty of exclusion may be enforced by display of the Black Flag.

Action: do as it says immediately.