Firewall reinforcements get counter sinks to fit the dimples on the firewall. Lots of countersinks but no issue making them on the drill press. Then the parts are back riveted to the firewall sides and finally the top piece of the firewall skin is partially riveted on along with a reinforcement bar. A small bead of tank sealant is used prior to putting these parts together to seal the firewall so fluids and fumes do not enter the cabin. Later, more tank sealant is used when attaching the tunnel parts to this assembly.
