Trimming the inspection plates to match fit the inner skins. The 4 Inner skins have the nutplates attached and are not interchangeable with each other. Typical issues are water freeze thawing between the skins, delaminating, and corroding the skins severely enough to be replaced. Tanks with a history of attempted re-seals may have fuel traveling between the skins. The only proper way to repair this condition is to dismantle the tank and sometimes replace the skins.