Abstract: An insert for installation in a hole therefor in a parent material by relative axial movement of the insert and material with or without the aid of heat, such as by high frequency vibration, wherein the insert has a series of external uniform diameter annular peripheral taper portions each tapering down towards the leading end of the insert and longitudinally serrated to provide projections for barb-like retention of the insert in the hole; and a reduced diameter pilot portion at the leading end of the insert having an external lip of substantially less diameter than that of the taper portions, which lip engages the hole in order to assist initial axial alignment and contact of the insert with the hole at the commencement of installation of the insert therein.