Multi 21
Used by mainly by Formula 1 teams, the internal code translates as an 'order to maintain position'. It is a rule that cannot be broken, and allows the racers to save their cars by driving more relaxed in the knowledge that they will not be attacked. It was used by both Red Bull and Mercedes teams during the Malyasian Grand Prix in 2013. While the rule was obeyed by Lewis Hamilton and Nico Rosberg of Mercedes, Sebastian Vettel disobeyed it to overtake then race leader Mark Webber, both of Red Bull.
Webber: Multi 21, Seb, multi 21.