They indeed have a cotter pin. You can get the pins at police uniform shops, as the metal buttons on uniforms work the same way. The metal buttons have a loop on the back. Just slip them through a wee tinu button hole and slip the cotter pin through. It works even better if you put a metal disk between the button and the cotter pin, but the disks are harder to find. Ask wlverine to see a photo of his PC. I used the cotter pins on it.