On a shape-changing call (usually from a Box to a Line or Wave),
the idea is to maintain the center point between the pairs of dancers.
In the above example, dancers

and

finish such that their center point is the original center point between dancers

and

. Similarly, dancers

and

finish such that their center point is the original center point between dancers

and

(which just happens to be the original starting position of dancer

).
EN: 135