Intending to be helpful, some callers routinely say phrases such as
  
Centers Slip or 
Centers Slither when they really mean
  
Slip or 
Slither, respectively.  This can be misleading
  because normally the word 'Centers' identifies and activates the Center 4 dancers only.
  If the (active) Centers are 
not in a Wave or other applicable 4-dancer
  formation, then they can't do a 
Slip or 
Slither.  For example,
  from Parallel Waves, consider the call 
Centers Slip: the caller identified
  the Centers, who are in a Box; but 
Slip from a Box makes no sense.
  Also, from formations such as Twin Diamonds or a Tidal Wave, 
Slip 
  (or 
Slither) and 
Centers Slip (or 
Centers Slither) are
  different calls! 
EN: 150