Section 28. Except as provided in the last paragraph of this section, the names of persons who apply for employment in the labor service of the commonwealth and of the cities and towns shall be registered and placed, in the order of the dates on which they file their applications, on the registers for the titles for which they apply and qualify. The name of any such person shall remain on such register for not more than five years, subject to a renewal of application pursuant to this section. Such person shall continue to be eligible for appointment from any such register and shall maintain his place on such register if he renews his application during the six months immediately prior to or during the six months immediately following the expiration of his five year period of eligibility. Such continuing eligibility shall have a duration of not more than five years after the date of expiration of the original five year period. A renewal filed later than six months after such expiration date will not be accepted, and the applicant who filed such late renewal will be required to file a new application and will be placed on the register as of the new date of registration.

During his period of eligibility, any such person may add titles for which he qualifies, in addition to those for which he originally applied, to his application for employment in the labor service. Eligibility for appointment to such additional titles shall continue for the remainder of the period of eligibility for the titles for which application was originally made.

An appointing authority may include in a requisition for laborers a statement that the work to be performed requires young and vigorous persons. The administrator, after investigating such statement and being satisfied that it is true, may establish an age limit and certify only those persons whose age is within such limit.

The names of veterans who apply for employment in the labor service shall be placed on the registers for the titles for which they qualify ahead of the names of all other persons. The names of spouse or surviving parent of veterans who were killed in action or died from service connected disability, incurred in wartime service, who present proof from official sources of such facts, satisfactory to the administrator, and who have not remarried, shall be placed on the registers for the titles in the labor service for which they apply and qualify above the names of all other applicants but below the names of veterans.