From Tandem Couples, a Mini-Wave Box or the 2 x 2
  T-Bone obtained from a Mini-Wave Box after Leaders 1/4 Out.
There are two slightly different definitions of Boomerang depending upon
  the starting formation.
- From Tandem Couples: Leaders Zoom as Trailers Circulate and
    Trade.  Ends in Facing Couples.
 - From a Mini-Wave Box or other applicable 2 x 2 formations:
    Leaders Zoom as Trailers Scoot Back (Extend, Trade, and Extend).  A
    Mini-Wave Box ends in a Mini-Wave Box.  This use of Boomerang can
    be fractionalized into halves.
 
Note: From Tandem Couples, everyone can Roll; from
  other formations only the original Leaders can Roll.