An oxidized nail — the nail piercing the metal cladding in the left hole is oxidized. Beyond the empty nail hole, the two nails on the far right do not appear affected. The right-most nail is through a strapping overlap. There is a tiny gap of un-caulked seam just above the residual foam upper border. This photo also shows the dark grey foundation concrete still curing just under the Airform rope. (Chris Ecker)