Source : Webster's Revised Unabridged Dictionary (1913)

   4. A measure of length, being two inches and a quarter, or
      the sixteenth of a yard.

   {Nail ball} (Ordnance), a round projectile with an iron bolt
      protruding to prevent it from turning in the gun.

   {Nail plate}, iron in plates from which cut nails are made.
      

   {On the nail}, in hand; on the spot; immediately; without
      delay or time of credit; as, to pay money on the nail.
      ``You shall have ten thousand pounds on the nail.''
      --Beaconsfield.

   {To hit the nail on the head}, to hit most effectively; to do
      or say a thing in the right way.