So, you just ordered 200 boxes from USPS because they were free and you've probably used close to none. Heres a neat project I made on how to utilize the smaller boxes. Don't have any boxes? Go to USPS.com and order some, they're free.

Step 1: Get a Box, Razor, and Packing Tape

In this picture I have two boxes because I wasn't sure how much I needed, get two in case you need another. Then get a razor and/or scissors and packing tape from officemax, walgreens or where ever.

Step 2: Tape Up the Box

Next get the box so its fully folded up, as if you were about to ship something in it, but instead tape everything top and bottom and then the sides (See pictures for reference) This step makes it almost air-tight.

Step 3: Grab Your Vent

Get your vent out of its hole and close it and put it on the top or bottom, doesn't matter, then outline the part where the air comes through. I would put it more to one side if the vents on a wall.

Next, cut the outline you just made with your razor and pop out the cardboard.
Keep the cardboard that you just cut out, you will need it later.

If you wish put the vent in the hole to test if it fits... Mine does, perfect fit =)

Step 4: Put It Over Your Vent and Cut a Hole

Simply put it over your vent and check if any air comes out the top or sides, it should a little at the bottom. Now mark with the razor or a pen which way you want the air to go in the vent, I want mine to come out the side pictured so I cut a little gash in the middle of it.

Next I got my razor and just cut a hole, didn't really madder on what size, but its pretty big on mine. Once again, keep this peice.

Step 5: Make a Ramp

The next step involves making a ramp, to help guide the air out to the hole you just made. Use the two peices that I told you to save and tape them inside any way you wish, you may look at my pictures to see how I did it.

This is also the step when I realized that I needed to charge my digital camera and it died, so I whipped out my webcam and got us 50% worse quality photos. Oh goodie.

Step 6: Put It on Your Vent

Now it is time to put it on your vent and enjoy the air being pushed not up but in the direction you made your vent cover go in. You might want to tape more in the inside to help the air flow more better. Heres a picture of mine with a flashlight since I was using my webcam =(

This was my first instructable, any suggestions and comments would help =)