A fastener is configured to affix a first article such as a picket to a second article such as a rail to form a railing or balustrade. The fastener includes a first engaging surface having a maximum diameter configured to engage an interior surface of an opening in the first article and a mating surface configured to mate with the second article. The first engaging surface can have shape selected from cylindrical, ellipsoidal, conical, elliptic conical frustum, pyramidal frustum, and ball and other shapes having cross-sections of rectangular, pentagonal, hexagonal, octagonal and other regular polygons having at least four sides such that good engagement is obtained and the fastener is hidden from view in the assembled railing.