Source : Webster's Revised Unabridged Dictionary (1913)

   2. Course of thought; thread of narration. [Obs.]

            Let me resume the file of my narration. --Sir H.
                                                  Wotton.

   {File firing}, the act of firing by file, or each file
      independently of others.

   {File leader}, the soldier at the front of any file, who
      covers and leads those in rear of him.

   {File marching}, the marching of a line two deep, when faced
      to the right or left, so that the front and rear rank
      march side by side. --Brande & C. 

   {Indian file}, or {Single file}, a line of men marching one
      behind another; a single row.

   {On file}, preserved in an orderly collection.

   {Rank and file}.
      (a) The body of soldiers constituing the mass of an army,
          including corporals and privates. --Wilhelm.
      (b) Those who constitute the bulk or working members of a
          party, society, etc., in distinction from the leaders.