A fastener consisting of a cylindrical expander shell with longitudinal sections of its shank removed. This design allows the shell to be pulled toward the head and form anchoring legs on the blind side of the assembly. The shell has a tapered, sharp point at one end and a flanged collar at the opposite end with an opening sufficiently large enough to allow a screw to pass to the threaded opening. The flange of the collar has prongs which dig into the bearing surface at the front end of the assembly, a pan head screw, and a flat washer.