Description from the dance "Back to Back":

First couple dances a figure of eight on the side of the dance, around their own corner positions, starting with right shoulder to first corner  
while second and third men, and likewise second and third women, dance consecutive back to backs on the side of the dance. Second and third couples begin by passing right shoulders on bars 17-18 and left shoulders on bars 21-22. 

Note: besides the above way the Formation may be danced in a "mirrored" way (as in the dance "Still Together") with the dancing couple starting down and out and the corner couples dancing Back to Back accordingly.