In a Longwise set, the rectangle becomes a parallelogram with Crossing (Across the set) replaced by Crossing Diagonally. This Figure involves only 4 Dancers rather than the 6 in the full Figure: the Dancing couple Finish opposite their Starting Positions. Either First or Second Corners, but not both, are involved; the Corners Finish diagonally opposite their Starting Positions, i.e., they Exchange places.
The diagram shows, as an example, bars 29-32 of Bratach Bàna: first, the Dancing couple, in 2nd Place on Opposite Sides, Cross diagonally By the right, the Lady going Down, the Man going Up, and so Exchange places with her/his Partner's First corner position; then they Cross up and down on the sides By the left to reach 2nd Place on their Own sides.
Note that, in a Longwise set (the most common usage), Half diagonal rights and lefts differs from the simpler Half rights and lefts in that the Dancing couple always Cross with a Corner, never with each other.