I love my iPhone, so I'm also paranoid about scratching it. However, I can't stand those big plastic cases, and came up with a way to make thin Duct tape cases for several gadgets. This instructable also has an optional card holder on the outside of the case.

Step 1: Materials

You will need:
1. iPhone
2. Scissors
3. Duct tape!
4. A needle and thread
5. Sock with an ankle long enough to hold an iPhone (thinner fabric is better)
6. A square plastic bag

Step 2: Measuring and Cutting Your Sock

Once you have your sock, slip the iPhone into the ankle, and stop when the top of the phone is flush with the end of your sock. Use chalk or an eraser to mark where the bottom of the phone is in the sock, and then cut across the ankle a few millimeters below your mark. Cut lower if you want your phone to sit deeper in the finished case.

Step 3: Sewing the Sock Together

Once you have your cut sock, take the phone out, and sew straight across the cut end. I'm horrible at sewing, so I just whip stitched across.

Basically, after threading the needle, you double the thread back on itself, and tie a knot about a foot away from the needle. Push the needle though both sides of the sock, and then repeat on the same side, about 2 millimeters over. When you get to the other side of the sock, tie another knot to keep the thread from coming undone. I also turned the sock inside out when I was done.

Step 4: Taping the Sock

Slide your phone back into the sock, making sure it sits at whatever depth you want. Keeping the phone inside the case insures that the case is the right size and shape. Keep your new seam along the bottom of the phone to keep things less lumpy.

Cut a piece of duct tape about an inch longer than what would be needed to wrap around the case (horizontally, the short way). With the screen side of the phone up, stick the ond of your strip of duct tape just left of center, and have the edge of the tape lined up or just below the opening of your case. Then wrap it around until it overlaps a little bit. Be careful not to make any folds in the sock.

Wrap two more strips of tape around the case, each should barely overlap the one above it, and the bottom strip should be around a centimeter above end of the case with the seam.

Step 5: Closing the Bottom of the Case

Cut another piece of tape with about four centimeters longer than the base of the case. Stick the case to the middle of the tape, and then stick the short ends to the thin sides of the case. Stick the long ends of tape to the flat side of the case, and gradually stick more of it on- slide over to the side of the case, and pinch the flaps of tape together. Make these little flaps on each corner, and then cut them off near the base. Use two small pieces of tape the cover these cuts, otherwise they may come undone.

Step 6: Adding the Card Holder

Using your card as a template, cut out a rectangle of your plastic bag- I used the corner, keeping the layers together. However, only one layer is needed. Lay the plastic bag on the flat side of your case, and attach it using strips of tape like in step four. Cover all the plastic with horizontal strips.

Step 7: Finished!

Your case is pretty much done now, but you can add one long strip of tape that goes down both sides of the case to cover up all the other tape edges. The iPhone by itself is about 12.5mm thick, and with this case, it is 16.5mm thick. without the extra tape and card holder, you can get it a lot thinner. If its tight at first, don't worry; it will stretch and become softer over time. Duct tape and socks make excellent cases for most gadgets- I've also made cases for PSPs and iPods.

If you have any ideas to add, please post them in the comments; I'm always trying to improve something I use so often!