This group is the most unusual pieces I have. The back two use a small strain insulator. Wish there was a name on them but I have found no manufacturer yet who sold them. The first two in the bottom row are called CB Knobs and were sold by Joslyn Mfg. Co. Don't know if the name was their purpose or not. The first is a two groove and second is single. Both are embossed Patented on the sides. The last one is an unusual three groove spool and uses a medium sized screw eye. No markings on this piece either so can't identify a manufacturer.