NASCAR Racing: Another rule question about slower cars, rule question, flagman

Question
In a race where their are going to be slower cars, is their a rule or common courtesy that tells where the slower cars have to run on the track when the leaders are coming. Obviously if the car is not a lap down yet they can still race to stay on the lead lap. But the question pertains to lapped cars.
Thank you

Answer
Hi again,

There is no offical rule for the slower cars, however, it is common courtesy to move out of the groove to let the leaders by.  If a slower car blocks repeatedly, the flagman will black flag the car and NASCAR will tell him to get out of the way or he will not be scored.  But this is only in an extreme case.  Most of the time, if the blocker blocks, the leader will move them out of the way.
Hope I helped!
Coy Jordan