Section 1007. When third-party practice allowed

After the service of his
  answer, a defendant may proceed against a person not a party who  is  or
  may be liable to that defendant for all or part of the plaintiff's claim
  against that defendant, by filing pursuant to section three hundred four
  of  this  chapter  a third-party summons and complaint with the clerk of
  the court in the county in which the main action is pending, for which a
  separate index number shall not be issued but a  separate  index  number
  fee  shall  be  collected. The third-party summons and complaint and all
  prior pleadings served in the action shall be served  upon  such  person
  within  one  hundred  twenty  days of the filing.  A defendant serving a
  third-party complaint shall be styled a third-party  plaintiff  and  the
  person  so served shall be styled a third-party defendant. The defendant
  shall  also  serve  a  copy  of  such  third-party  complaint  upon  the
  plaintiff's  attorney  simultaneously  upon  issuance for service of the
  third-party complaint on the third-party defendant.