The W-423 joint plates were fabricated earlier during the construction of the outboard leading edges. The joint plates are strips of aluminum sheet that are riveted between the leading edge skin and the inboard rib. They extend out from under the skin to the area under the fuel tank skin and are drilled to match the screw holes in the tank skins. This joint plate is fastened to the tank skin by screws in the final assembly to hold the two halves of the wing’s leading edge together.
In this build session, I needed to drill the matching holes in the joint plate, using the holes in the tank skin as a guide. Here are the tank and leading edge skins abutting each other on the wing. The joint between skins is the right edge of the silver strip with the blue protective vinyl removed. Notice that this joint is really tight, with almost no visible gap between the sheets of skin.
With the holes drilled, the next tasks are to dimple the holes for flush screws, drill rivet holes for the plate-nuts, and to rivet on the plate-nuts. Here is what the completed joint plates look like when installed on the leading edges. Then the tanks are installed, they will simply slide over the joint plates to be fastened with screws.