Vintage Vise Grip Clamp Plier Tool Locking Sheet Metal Welder USA.  I have seen this type of clamp used by the mechanics in the Boeing Company. Adjustment is made by adjusting the bolt to fit the material being clamped. The handle must be opened a little bit to fit . Then the handles is pressed together to make the grip.  To release pull the middle lever towards either one of the handles. Capacity 1 1/4".