"but its you are unable to use the clamping system inside the tool box. You will get some water through those holes so don't keep anything in there that can't get wet. This is an interim solution until the specified part becomes available."
The adopter part is suppose to bridge the gap from the head rail to the two holes of toolbox somehow. Meantime, I can plug the hole by using rubber and metal washer sandwiched by nut and bolt which matches the size of hole. That should keep it waterproofed.
