Unknown tool accessory

Was given a box of mixed tools today , but one item has me totally confused as to what it is, any help would be greatly appreciated.

That is a sideways clamp for use in a bench dog hole. You fit the round bar into a pre drilled dog hole and use it to hold the workpiece against other bench dogs. Search Google for benchdog images, that will help explain things.

Thanks Keith. I can see how that would work .