The Collaborative International Dictionary of English v.0.48:

Lock \Lock\, v. i.
   To become fast, as by means of a lock or by interlacing; as,
   the door locks close.
   [1913 Webster]

         When it locked none might through it pass. --Spenser.
   [1913 Webster]

   To lock into, to fit or slide into; as, they lock into each
      other. --Boyle.
      [1913 Webster]