The transfer of an employee in the skilled or professional service from one principal unit to another principal unit may be made only as follows: An employee may apply for transfer to a vacant position of the same classification or another classification of the same grade for which the employee meets the minimum qualifications; or An employee shall be considered among the eligible applicants for the vacancy if the employee complies with the provisions of §A(1) of this regulation, or when the employee qualifies as part of an approved Career Reinvestment Program as defined in COMAR 17.04.01. An employee in the management and executive services and a special appointee may apply for transfer to other positions of the same grade in those service categories only.