This is a basic, yet durable duct tape wallet that I have come up with using only index cards & tape. It holds 2+ cards, an ID/Driver's license, and assorted bills.
Step 1: Materials
You will need:
~Eight 3x5 index cards (seven if you don't want a strap)
~Clear packing tape
~Duct tape (any color; I used silver)
Step 2: Making the Back of the Wallet
Take two of the index cards, and cover each in a thin layer of duct tape, making sure that as little white as possible is showing. Then, keeping the cards about a centimeter apart, use two or three pieces of duct tape to tape them together. Flip over the whole thing and tape the cards together on the inside. Be sure to press down on the bit of tape between the cards in order to get it secure. This will be where your bill folds and other pockets are reinforced.
Step 3: The Bill Folds
In this step you'll be using what I refer to as "the bill fold method", which you will use to make all of the pockets on the wallet.
Start by placing an index card so that it overlaps with the right-hand index card (the taped up one). Next, place a strip of tape as in picture 2. Fold the edges of the tape over, bottom edge first, in order to secure the card. Use your scissors to trim off extra tape. Cover the index card with horizontal strips of tape that trail off over the right-hand edge, and fold over those edges so that the right side edge is uninterrupted between the original card and the newest one. Make sure that you leave the top edge open, otherwise you won't have a pocket. Repeat this with another index card on the left side, then use two strips of tape that span across both cards to fasten them together. Press down on the middle area (the centimeter bit) so that you end up with two separate bill folds.
Step 4: Making the ID Slot
Use "the bill fold method" to create a second bill fold on the LEFT HAND SIDE. Then, place your card down as in picture 2 and trace the two shortest sides with an ink pen. Then, cut out the area you traced, as in picture 3. Now, take a strip of clear tape and tape it inside the pocket so that the sticky side faces out, and the tape covers the inside "U" shape frame left from the cutout (I would put pictures for this bit, but you wouldn't be able to see the packing tape anyway). Then with a strip the same size (still clear tape), sticky side DOWN, line up the two strips to form a non-sticky, transparent window through which your card is visible.
Step 5: Making the Card Slots
Cut an index card in half, so that you have two thin strips (1.5x5). Use the bill fold method to position the first one a bit high up on the inside-right, as in picture one. Then, add a second slot at the bottom, as in picture three.
Step 6: Ces Fini!
And behold! Your wallet is done! use the leftover index card to make a strap if you want; It'll help keep the wallet shut when it's out of your pocket.