From a Wave-Based Triangle or Tandem-Based Triangle.
Move forward to the next Triangle position, changing your facing direction 
  (by turning toward the Center of the Triangle) 90° or 180° as 
  appropriate to change a Tandem-Based Triangle into a Wave-Based Triangle or vice-versa.
| From Wave-Based Triangles: 
 | 
| 
From Tandem-Based Triangles: | 
Notes:
- 
Reshape The Triangle feels a lot like a Split Counter Rotate 1/4
    working to Triangle footprints.  In practice, you can dance
    Reshape as Triangle Counter Rotate 1/4 to footprints, and
    one of the dancers Roll in order to form a Triangle of the other type.
    From a Wave-Based Triangle, Reshape feels like Triangle Counter
    Rotate 1/4, original Apex dancer Roll.  From a
    Tandem-Based Triangle, Reshape feels like Triangle Counter
    Rotate 1/4, new Apex dancer Roll.
- 
If you start in a Tandem-Based Triangle, you must end
    in a Wave-Based Triangle and vice-versa.
- 
From normal (not Facing or Funny) Triangles, the facing direction
    of the Apex position does not change.
- 
Maintain the handedness of the Triangle.  If you start in a R-H
    Triangle you must end in a R-H Triangle.
| 
 |   |  |   |  | before 3 By 1 Triangle Reshape
 |  | after 
 | 
 |