A coach or infield leader will yell double cut.  Double cuts are needed when a ball is hit to the fence and there is gonna be a long throw to a base.  On a ball hit to the left field gap and the play is expected at 3rd base.  The SS will be the lead relay guy and 2B will be the trail man.  The pitcher will back up the throw at 3rd base.  The 1B will trail the runner to 2nd and then be the coverage for 2nd.