Most Adjustable or "Crescent type Wrenches" have a screw thats really a small shaft that goes thru the adjustment knob that has a cut on one end to use a flat bladed screw driver and a thread on the other to hold it in.
For some reason this looks like to me the center focus adjustment post on an old pair of either opera glasses or binoculars and the adjustment knob would go over the threads to adjust the focus?