Section 2A. In the conduct of examinations they shall make uniform requirements for all towns, which may be revised from time to time, as circumstances require. They shall grant a credit of five per cent to the examination standing of each applicant who is a veteran, as defined in clause Forty-third of section seven of chapter four. Said examinations shall be sufficiently frequent to give ample opportunity for all applicants to be thoroughly and carefully examined, may be written or in practical work, and may be supervised by one or more of the examiners, but no license shall be granted without the sanction of the examiners. The examiners shall promulgate regulations to determine the allowable education and work hour credits for veterans and military personnel.