What is this for?

Kalifornia emissions crap. Bunch of fuel line tubing attached under there. 4 lines if I can remember correctly, and it goes thru a slot in the framerail back to the gas tank. Make a flat metal plate with a foam gasket with holes in it that line up with the existing screw holes in the trunk extension. Then screw it in over the hole using the same type button head screws that holds on the rubber trunk floor gasket that goes around the fuel filler neck.