I was putting in some b-quite extreme in my turnk of my 02 altima. I noticed on the left side opposite the jack there is this little cut out with a plastic peice which has a flap attached to it. I am guessing this is so air can get into the trunk in case someone is looked in there, but i am not sure. I was thinking about covering it with b-quite extreme but I said i better waite until i find out what it is for. I would think that a lot of base probally exits there instead of coming into the cabin.