Come into the pits immediately for consultation. Normally, this flag is waved at an individual car, either because it has a mechanical problem or has broken a rule. Waved in combination with a red flag signals the end of a practice session.
Cars that refuse to acknowledge the black flag are shown this flag, which means NASCAR will no longer score them until they come into the pits for consultation.
Pay attention to your mirrors, because a faster car is approaching from behind. Contrary to popular opinion, this flag does not make it mandatory that slower cars must move over for the leader of the race. This flag gets a workout at tracks like Bristol and Martinsville, where traffic becomes a major factor.
Used only on road courses by corner workers, held or waved to signify debris or slippery conditions ahead.