Rule 2958 - Execution, Notice Of Entry Of Judgment(b) No writ of execution to sell real estate shall issue upon a judgment entered on an instrument accompanied by a mortgage on real estate until twenty (20) days after the affidavit has been filed, certifying that the written notice has been served personally or sent by registered mail. Where the owners of the mortgaged premises, or obligors, are not known or their whereabouts are unknown, the affidavit shall state what was done to ascertain such information.