There is not much direction or drawing documentation for the corner ribs. I eye-balled it and marked it with the sharpie. I then off the ends with the band saw and took it from there with the sander and scotch brite wheel. The rib fit the edge of the skin pretty well but not perfectly. I lined it up as best as possible and clamped it in place. I then slid it over to the edge of the workbench and got down on the floor to drill through the skin holes into the rib.
