PROMOTE

***** PROMOTE *****   

Command : promote
Usage   : promote k | b | r | q

NOTE:
  This command is obsolete.  It is kept because some client
  programs and old computer programs still depend on it.
  To promote to something besides a queen, use "=" notation,
  as in "e8=n".

Here is the rest of the old "promote" help file:
  Sets the promotion type. When a pawn reaches the 8th rank,
  it will be promoted to a queen by default. You can change
  this to a knight (k), bishop (b), or rook (r), by typing
  "promote piece" where piece is k, b, r.  You must type
  this BEFORE moving the pawn.  Your new promotion choice
  remains in effect for the rest of the current game. You can
  change the promotion type back to a queen with "promote q".

  Yes, we know "k" is a dumb letter for knight, and "n" would be 
  better :)