Civil Service Personnel Rule 15
15. The Ministries and service personnel organizations may initially appoint external persons to the following posts:
(a) general service staff grade (1);
(b) clerical staff grade (1);
(c) technical staff grade (1) and (4);
(d) professional staff grade (1), (2) and (3);
(e) management staff (economic) grade (1);
(f) management staff (administration, social) grade (1).