Red's idea was that, from column formation, each couple would replace the couple ahead by walking forward in single file. His call was "Eight Circulate Single File as a Pair." Today, this move is called Single File Circulate Two Positions. From column formation, the move itself goes like this: Dancers move forward to assume the position and facing direction of the dancer ahead, Lead two dancers in each file of four will "turn the corner" into the other file, as all the others walk straight ahead.
"Red" Porter 1968
This definition is from The Handbook of Modern Square Dancing by Jay King.
It is provided here for informational and educational purposes only.