What is this thing?
 

What is this thing? There's one on both sides of the trunk behind the liners. There are two thin flaps on each that are causing an absurd amount of rattle from my subwoofer.

http://imageshack.us/a/img201/5788/98350649.jpg

http://imageshack.us/a/img138/184/43473153.jpg

Vents to allow the air to escape when you close the door/trunk.

simple enough. thanks!

I always wondered what those were. Whenever I saw a car with no rear bumper I noticed those weird flaps and couldn't figure out just what the heck they were.

They also allow air to escape when you have the heat/AC running. Air has to exit the car somewhere when the blower is sucking it in, they are there to prevent positive pressure from building up inside the vehicle.

I wondered for years what those were for. always noticed them when I did amplifier installs. thank you

Just learned something myself!

Roach traps.