Section 54(4) in M.P. Industrial Relations Rules, 1961
(4)Where there are numerous persons as parties to any proceeding before Labour Court, the Industrial Court or a Board and such persons are not the members of a trade union or an association, a Labour Court, the Industrial Court or a Board as the case may be, shall cause the service of any notice, process, summons or order to be made by affixing the same at or near the main entrance of the undertaking concerned. A notice, process, summons or order served in such manner shall be deemed to be duly served on such employees as cannot be ascertained, found or served otherwise.
