Section 20(2) in Industrial Disputes (Central) Rules, 1957
(2)Where there are numerous persons as parties to any proceedings before a Board, Court, Labour Court, Tribunal or National Tribunal or an Arbitrator and such persons are not members of any trade union or association, the Board, Court, Labour Court, Tribunal, National 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 establishment concerned. (3) A notice served in the manner specified in sub-rule (2) shall also be considered as sufficient in the case of such workmen as cannot be ascertained and found.
