Abstract: A fastener for securing an object to a concrete mounting pad is provided with an elongated interiorally threaded annular core. The upper section of the core is of a cylindrical outer configuration while the lower section is tapered as a fustrum of a cone to an overhanging ledge at the lower extremity of the upper section. An expansion device includes two half rings, initially held together by tape. The expansion device encircles the conical fustrum just below the ledge. Upward force upon the core pulls a larger portion of the fustrum through the half rings, thus directing them radially outward and securing the expansion device and the core captured by it in an anchor shaft in the concrete. Conversely, downward force on the core removes the radially outward force on the expansion device and allows the anchor to be driven to the bottom of the anchor shaft bore.