code: private void rightShift(
      int           ix)
    {
      for (int j = rightMostIndex(); j >= ix; j--)
        _nodeKey[j+1] = _nodeKey[j];
    }
docs: Open up a slot for a new key by shifting keys right to make room.
  
  <p>We are inserting a new key into a node that is not currently
  full.  There is at least one vacant slot.  We open up the correct
  slot for the new key by shifting all other keys right.</p>