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We have a floor to ceiling hall cabinet, built in place, in a 1940’s home. When you pull out the bottom drawer you see the hardwood flooring underneath. Upon doing this for the first time last week, we found the floor to be lined with aluminum foil. There were no mouse droppings or even any dust per se. what could be the reason for this? There is a moisture barrier between the hardwood and the subfloor, as I’ve been into the floor in other rooms for repair. Been in the house ten years and had never pulled the drawer out prior.