This is a great one handed edge clamp.
You put the large "C" shaped gadget over the wood and begin to turn the handle.
The upper and lower clamping pads move in to grab the main sheet.
Once they grip, then the side clamp moves forward to secure the trim on the edge.
When they have all gripped, then you can add force, up to 500 pounds of clamping power, all with one hand.
It is the Professional One Hand Edge Clamp from Bessey.