Swing to a Column

From a generalized 1/4 tag (usually a right-handed 3/4 tag): centers Trade and Roll and then walk forward, passing right shoulders, to become #1 and #2 of a column. Ends Divide, Touch, and do a sort of Flip the Line 1/2 to become #3 and #4 of that column. All passes are right shoulder, even if the starting formation makes that awkward.

\sxvBBBs{...,g3n,g4n,b4s,...,b1s} \syhlines{b3e,g1e,b2e,g4e}
3 1 4 2 4 2 1 3 3 1 1 3 2 4 4 2
before Swing to a Column after