Centers (or designated dancers) slide sideways toward the 
  Outsides (or non-designated dancers) who move into the vacated space.
Notes:
- 
To avoid collisions, the Centers (or designated dancers) may
    have to temporarily move forward or backward to move around
    the other dancers.
- 
Nobody changes their facing direction during a Lateral Substitute.
- 
The difference between Substitute [C1] and Lateral Substitute
   is the facing direction of the Centers (or designated dancers).  
   On a Substitute, these dancers move forward or backward;
   On a Lateral Substitute, at least one of these dancers moves sideways.
Substitute [C1]:
 From Generalized Columns.
  Centers raise joined hands to make an arch and (moving toward the nearest 
  Outsides) move forward or backward as the Outsides move into the Center.
  The traffic pattern has the Centers moving around the Outsides.  
  Substitute exchanges the
  Centers with the Outsides.  Nobody changes their facing direction during this
  call, and, in practice, dancers rarely make the arch.  From Tandem Couples,
  Lead Couple arch & back up as Trailing Couple Steps Ahead (Circulate).