be used to join two or more parts together pin 21 further includes retention means 30 in the embodiment of fig1 means 30 is a helical thread with a major diameter forming a crest 31 and a minor diameter forming the bottom 32 of a helical groove the thread extends to the second end in a conventional manner according to this invention the thread is modified by providing a reduced crest diameter between the major and minor diameter to form a modified thread section 33 disposed between at least one complete convolution 34 at the second end and at least three fully formed convolutions 35 on the side toward the head which must project beyond the material grip range of the pin collar 22 has a body 40 with an internal passage 41 a counterbore 42 will face the workpiece to accommodate any unthreaded portion of the shank which protrudes beyond the workpiece an internal thread 43 is dimensioned to make a proper fit with the unmodified portion of the thread on the pin in the preferred embodiment of the collar a drive section 44 has a wrench engaging array 45 of surfaces preferably hexagonal a frangible reduced section 46 joins the drive section to the remainder of the body this is the well known hilok fastener produced by hi shear corporation of.