From column formation: Lead dancer of each file promenades around the end of the adjacent column to the next position in the square to face in. The other three dancers in each file single file Circulate forward until shoulder to shoulder and all arm turn 3/4, then step ahead where the center person of the line of three joins right hands (left hands if the arm turn was by the left) with the lonesome outside dancer. Finishes in Three and One Lines.
This definition is from The Handbook of Modern Square Dancing by Jay King.
It is provided here for informational and educational purposes only.