When doing calls within Blocks, traffic patterns vary.  For simple calls that
  do not require interaction with more than one other dancer at a time, execute
  each part of the call within the footprints of your individual Block (e.g.,
  Square Thru, Touch 1/4).  On more complicated calls (e.g., In Your Block Square Chain Thru),
  start the execution of the call to the footprints of your individual Block, and when it becomes
  necessary to interact with more than one dancer at a time, the dancers closest
  to the center of the set should cross the center line to join the other dancers
  in their Block to complete the call on
  each side.  Once the call is completed, re-establish the Block
  footprints by having the appropriate dancers move to re-create the original
  slant of the diagonal (i.e., NW-SE or SW-NE) and the other dancers move to
  appropriate Block footprints.  Note: Some dancers need not move at all to
  re-establish footprints (typically, only four or six dancers need to move)! 
EN: 190