I had a flat tire the other night (a nail, probably courtesy of Home Depot) and when I pulled out the donut spare, I noticed two black rubber plugs in the spare tire well. Turns out they plug a couple of holes (maybe 1-2 inches each?) that are open to the ground. Does anyone know what these holes are for? I figure they were just for manufacturing convenience, but I wondered if there was any more interesting reason for them.