This call is difficult because the precise definition, with parts, is sometimes
violated by some concepts, and replaced by something related to its "feel".
It is usually done from a completed DPT. Ends 1/4 right, Counter Rotate,
and Twosome Drop In. Centers Shakedown, Veer Left, and As Couples Extend.
\sxvlines{g4n,g1n,b3s,b4s}
\sxvlines{g4e,b1w,g1w,b4w}
\syhDBDs{g2n,g3e,b3e,b2s}
\sxvlines{g3e,b3e,b2w,g4w}
before Countershake
1/3
2/3
finished
It has the feel of a Concentric Shakedown and solid box of 4 Touch. This is sometimes
used in, for example, 3x3 Countershake from a 2x6 matrix completed DPT.