A Trapezoid is a Distorted 2 x 2 that can be formed from a normal
  2 x 2 after any two adjacent dancers each move
  a distance of one matrix position directly away from each other. 
 From a 2 x 4, there are two Trapezoids.  The Ends of one side work with
  the Centers of the other side within a Distorted Box. 
Notes:
- 
 The traffic pattern for some Trapezoid calls can be horrendous.  Use
    Stars as necessary and try to get to your ending position without
    colliding with any other dancers. 
- 
 Calls must end on original Trapezoid footprints.  Shape-changing
    calls are not allowed. 
| 
 |   |  |   |  | before Trapezoid Couple Up
 |  | after 
 | 
 | 
| 
 |   |  |   |  | before Once Removed Trapezoid
 Counter Rotate 1/4
 |  | after 
 | 
 | 
 See also Magic Line | Wave CONCEPT [C3B]
 which (from Parallel Lines) involves the same footprints, but dancers work within a
  Distorted Line instead of a Distorted Box.