carpet for a box built

Very true. Not to brag but my boxes dont have any mistakes. I mean I just built my 2nd and 3rd boxes. This time I used 5/8" MDF. I copied these boxes off the one I bought froma  friend. He sold me the box and the sub (which is the same exact as what I have except his is a dual 4 ohm, mine is single 4 ohm). Anyways, the box was made by the shop we bought our stuff from, so that box was made for that sub. He sold me the box and sub for $20. I copied the demensions, got 2 sheets of of 5/8" MDF at work. yesterday I built the boxes using 1 1/4" staples and liquid nails. I did not have any blowouts and everything fit together nicely. I then sanded off the glue and it looks good. I would still like to carpet the box just to give it that professional finish.

The carpet tezjet is talking about is needle punch.  You can't get it at home depot.  You'll have to get it at a fabric shop (they should know what your talking about).  The glue you want to get is at home depot by the fiberglass and bondo.  It is the super 77+ spray adhesive.  When you spray it wait about 5 minutes (what i do is spray it, smoke a cig and then come back)  by that time it will be tacky enough to start wrapping the box.  Make sure you wrap the box in sections only spray the glue where you will be wrapping then move on to the next section. 

The carpet is mainly for looks.  If the carpet gets wet it will sink through the carpet and get the box wet.  You are right about the real protection is the car not the carpet.