From any Line of 4.
Centers Cross Run as Ends Run.
A Two-Faced Line ends in a Wave and vice-versa.
Notes:
- 
According to the CALLERLAB definitions, the Centers pass outside
    of the Ends as they Cross Run.
- 
Cross Roll To A Line | Wave is almost always called from a Two-Faced Line.
- 
From a R-H Two-Faced Line, Cross Roll To A Wave feels like a
    Turn & Deal and Step To A Wave.
- 
The caller usually says Cross Roll To A Wave when the ending
    formation is a Wave, and Cross Roll To A Line otherwise.
- 
Everybody moves toward the Center of the Line.
Switch The Line [C1] (Roger Chapman 1969):
 From any Line of 4.  Centers Run as Ends
  Cross Run.  A Wave ends in a Two-Faced Line and vice-versa.
Run Wild [C4] (Tim Ploch):
 From any Line of 4.  Cross Roll To A Line twice.