Section 22(2) in The Bihar Industrial Disputes Rules, 1961
(2)Where there are numerous persons as parties to any proceeding before a Board, Court, Labour Court Tribunal or Arbitrator and such persons are not members of any trade union or association, the Board, Court, Labour Court Tribunal or Arbitrator, as the case may be shall, where personal service is not practicable, cause the service of any notice to be made by affixing the same at or near the main entrance of the establishment concerned.
