Good auction on Saturday, I had figured what this item was, but apparently no one else did. I watched and it ended up with the table cleanup group along with other tools and I picked up the lot for $3.00. The socket fits over the rollers, it is square inside with rounded corners and the flat side goes toward the block or whatever. The sizes are 5/16, 3/8, 7/16 and 1/2" for studs of that size. When the 1/2 inch drive socket is turned the rollers pinch the stud and remove it. The box even has some of the original label.
