certificate, stating that because of some physical defect, mental unsoundness, or moral disqualification, particularly specified, said eligible would be incompetent or unfit for the performance of the duties of the vacant position, and if said officer shall sustain such objection with evidence satisfactory to the Commission, the Commission may certify the eligible on the register who is in average percentage next below those already certified in place of the one to whom objection is made and sustained.

6.  Certifications for appointment of persons for service in or on direct detail from any Department or office in Washington, D.C., shall be so made as to maintain as nearly as possible the apportionment of such appointments among the several States and Territories and District of Columbia upon the basis of population, except to appointments in the Government Printing Office, to the position of printer’s assistant, skilled helper, and operative in the Bureau of Engraving and Printing, to positions in the post quartermaster’s office, in the pension agency, and other local offices in the District of Columbia, and to the positions of page and messenger boy and apprentice or student.

7.  Within any part of the service to which promotion regulations have been or may hereafter be applied certification of those eligible to original appointment shall not be made for filling a vacancy in a position above the lowest class in any grade whenever there is any person eligible and willing to be promoted to said vacancy:  Provided, That a vacancy in any position requiring the exercise of technical or professional knowledge may be filled by original appointment.

  8.  When two or more eligibles on a register have the same average
  percentage, preference in certification shall be determined by the order
  in which their applications were filed.

9.  For filling vacancies in positions outside of the District of Columbia and in positions in the pension agency, the depot quartermaster’s office, and other local offices in the District of Columbia the territory of the United States shall be arranged in such sections or districts as the Commission may determine, and an eligible shall be certified in his order to vacancies in the section or district in which he resides, and, upon his written request, to vacancies in any one or more of the other sections or districts:  Provided, That in the custom-house service, post-office service, or internal-revenue service an eligible shall be certified only to vacancies in the customs district, post-office, or internal-revenue district where he was examined.

10.  In any part of the service in which the employment of substitutes is not prohibited by law there may be certified and appointed in the manner provided for in this rule only such number of substitutes as are actually needed for the performance