fastener systems for securing an object to the surface of structure , and methods for forming the same . shafts of fasteners have threaded ends which are to be embedded in holes formed in the structure and which are filled with a securing agent . for greater pull - out resistance the holes can be enlarged at their internal ends , either by molding or by breaking out the walls of the hole ends with a special tool . a lubricant coating the inserted shaft end permits withdrawal of the fastener shafts . in one embodiment , the external end and the internal end of the shaft are reversely threaded . a cap nut on the external end has a compressible pellet therein . initial threading downward of the cap nut tightens the nut more securely against the secured object , and further turning unthreads the fastener . a fixed head embodiment carries a cap at its internal end to prevent hardening securing agent from filling in under the shaft so that the shaft can be threaded deeper into the hole when the securing agent hardens .