The labor class shall include ordinary, unskilled laborers. Vacancies in the labor class shall be filled by appointment from lists of applicants registered by the civil service commission. Preference in employment from such lists shall be given according to regulations to be prescribed by the commission. The commission may establish separate labor lists for various institutions and departments. The commission shall require an applicant for registration for the labor service, before he can be registered, to furnish such evidence or to pass such examinations as it may deem proper with respect to his age, residence, physical condition, capacity for labor, sobriety, industry, and experience in the kind of work for which he applies.