Apparatus is provided having particular use in conjunction with setting of longitudinally extendable piling units for anchoring an offshore platform for subsequent use in drilling, production, completion and workover of a subterranean well. The apparatus is designed to be selectively movable within the base of the piling, thereafter the unit is manipulated to urge a plurality of circumferentially extending segmented units to expandably engage within the piling base and, preferably, be locked therewithin, such that the piling may be positionably engaged along longitudinally extending legs of the platform. In a preferred embodiment, the apparatus provides an inflatable element which expands the segments for engagement with the bore of the piling. Alternatively, a modified apparatus utilizes a unit which is inserted within the base of the piling by means of a wire line or related apparatus. In still another form of the invention, a similar apparatus is provided in modified form on elements which are activated by means of spring loaded dog elements. A method also is provided for utilization of the present apparatus.