From double pass thru formation: Centers Pair Off and Roll. Trailers Divide, walk in front of the couple facing out to pass right shoulders with trailer from the opposite side, then turn a quarter to face in and Roll (turn a quarter more). Finishes in lines of four with centers facing out and ends facing in.
This definition is from The Handbook of Modern Square Dancing by Jay King.
It is provided here for informational and educational purposes only.