4.117—Service of papers.
A copy of all pleadings, briefs, motions, letters, or other papers filed with the Board, shall be served upon the other party at the time of filing. Service of papers may be made personally or by mailing in a sealed envelope addressed to the other party. Any paper filed with the Board shall show on its face, or in the letter transmitting the same, that a copy thereof has been served upon the other party. When the other party is represented by counsel, such service shall be made upon him, and service upon counsel shall be deemed to be service upon the party he represents.