Abstract: A fastening system which may be used for fastening boards, particularly illuminated advertising signs, by the opposite edge thereof to a frame structure. In the fastening system, the fastenable edge of a board are (15, 16) are fitted with a fastening profile (8) having a substantially H-shaped cross-section. The fastening system includes a cross-sectionally substantially C-shaped locking profile (9) as well as fastener (10) for fixing the C-profile (9) to a tubular member (2), included in the frame structure and cooperating with the C-profile. The fastening of board edges (15, 16) to a frame structure can be effected by placing a leg (9a) of C-profile (9) in a groove between the legs (8a) of H-profile (8) extending away from the board in a manner that the H-profile settles against the tubular member (2). Thereafter, upon fixing C-profile (9) to tubular member (2) with fastener (10), the H-profile (8) is locked through the action of friction between the leg (9a) of C-profile (9) and the tubular member (2).