From a 2 x 4.
Do a total of four Split Circulates, except that when you become an
  In-facing Center do your next Circulate to your diagonal opposite position
  (crossing over into the other Box).  Exchange The Box can be
  fractionalized into fourths.
Traffic pattern: when crossing to the other Box, stay outside of those who are still in their
  original Box.  The In-facing Centers lead the Exchange and, from a normal setup, everyone
  else in their Box can follow them.
Dancing hint: Those leading the exchange should raise a hand to identify
  themselves so that the other dancers in their Boxes can follow them.
 Siehe auch Exchange The Triangle [C3A].