Marshals at various points around the circuit are issued with a number of standard flags, all used to communicate vital messages to the drivers as they race around the track.

Below is a guide as to what they all mean:

Chequered flag
Indicates to drivers that the session has ended. During practice and qualifying sessions it is waved at the allotted time, during the race it is shown first to the winner and then to every car that crosses the line behind him.
 

Yellow flag
Indicates danger, such as a stranded car, ahead. A single waved yellow flag warns drivers to slow down, while two waved yellow flags at the same post means that drivers must slow down and be prepared to stop if necessary. Overtaking is prohibited.
 

Green flag
All clear. The driver has passed the potential danger point and prohibitions imposed by yellow flags have been lifted.
 

Red flag
The session has been stopped.
 

Blue flag
Warns a driver that he is about to be lapped and to let the faster car overtake, should he disobey penalties can be awarded. A blue light will also appear in the cockpit. Blue lights are also displayed at the end of the pit lane when the pit exit is open and a car on track is approaching.
 

Yellow and red striped flag
Warns drivers of a slippery track surface, usually oil or water.

Black with orange circle flag
Accompanied by a car number, it warns a driver that he has a mechanical problem and must return to his pit.
 

Half black flag
Accompanied by a car number, it warns of unsporting behaviour.
 

Black flag
Accompanied by a car number, it directs a driver to return to his pit and is most often used to signal to the driver that he has been excluded from the race.
 

White flag
Warns of a slow moving vehicle on track.