When I caught up with Paul this afternoon he'd successfully measured and cut his raw material and had moved on to connecting the two pieces of sheet metal together. In this instance he needed to drill, dimple, squeeze, and fit.
Paul "dimples" the pieces. This pre-forms the metal to accept a flush rivet and increases the structural integrity of the union of the two pieces.
Paul then "squeezes" one rivet into each of the holes swelling the rivet to tightly secure the two pieces of aluminum together.
Paul then tests the fit to see what other adjustments may need to be made before finishing, priming, and painting the cover plate.