This is preceded by some kind of "Put Centers In" type of call that results
in a couple. That couple does a Cast Off 1/2, with the person who moved forward
doing the pushing.
\sxvlines{g4n,g1n,b3s,b4s}
\syhlines{b2s,b1s,g4s,g1s}
before Centers Left and Cast Away
after
This can also be called with an explicit fraction.