Lady and man meet, join right hand to right hand (sometimes both hands are joined) and raise those arms high. The man puts his back to the lady and starts to roll thru the arch, making a left face turn. Lady makes a left face roll with her back toward the man's back. When both have completed their roll under the arch, they have changed places and direction.
This definition is from The Handbook of Modern Square Dancing by Jay King.
It is provided here for informational and educational purposes only.