DannyW
Senior Member
Found this in my stepdad's workshop. If you turn the knob it spreads or closes those two arms at the other end. Made by Craftsman, the logo dates it between 1950 and 1964. It's 8-9 inches long.
My stepdad was a rock mason during the day and an amateur pool player at night, if that helps.
I know I could Google the picture but it's more fun to let another member show off his superior knowledge of tools.