In the 
Single version of a call, each dancer
  executes the movement that would normally be done by a set of two dancers
  within the normal version of the call.  For a call to have a 
Single version,
  it must be possible to group all dancers into sets of two, 
  in which the dancers in each set are always facing the same direction thoughout the
  given call.  The dancers in each set are usually dancing their portion of the call 
  As Couples, 
  In Tandem, 
  
Once Removed, or 
  
Twosome 
  (or some combination of these concepts).
  You can think of 
Single as replacing each set of two dancers with a single dancer located exactly
  half-way between the two dancers.  This single dancer then executes the given call 
  always staying on a path located exactly half-way
  between where the two dancers would be in the normal version of the call. 
EN: 36