Abstract: A fastener (1) comprises at least two fastener halves (3A, 3B) each of which comprises a main body (7A, 7B) and a finger (9A, 9B) depending therefrom, the finger (9A, 9B) being spaced apart from the main body (7A, 7B) so as to define a recess (13A, 13B) between the body (7A, 7B) and the finger (9A, 9B). The recess (13A, 13B) receives, in use, the finger (9B, 9A) of the other fastener half (3A, 3B) to fasten the fastener halves (3A, 3B) together. At least one of the recess (13A, 13B) of one fastener half (3A, 3B) and the finger (9A, 9B) of the other fastener half (3A, 3B) comprises a concave mating formation arranged to engage in use with a convex mating formation (15A, 15B) provided on the finger (9A, 9B) of the other fastener half (3A, 3B) or on the recess (13A, 13B) of the one fastener half (3A, 3B) respectively.