Duct tape wallets are non-optimal. The nature of the adhesive used on duct tape results in a wallet that will slowly slide apart based on the forces input to the wallet by your ass. After a year or so, depending on the ambient temperature of your location, the wallet will be falling apart and you will be building a new one. Besides, who needs all those pockets, a full length cash slot or other "wallet" features? In today's modern, RFID, credit-ready, cash-poor society a money clip with credit card and drivers license storage is truly the best wallet you will ever need. Any more storage and you will tempted to store receipts, ATM slips, business cards, and other sundry items in the wallet until you have a full blown case of "Costanza Wallet".
Enter the Innertube Wallet. As a Maker, geek, or otherwise shunned cheapskate, you doubtless have numerous blown bicycle innertubes, a few sheets of rusty 22 gauge steel, and any number of DOA hard disks and their attendant magnets. With such materials and a boundless enthusiasm for turning interminably stored junk into stuff you don't need, I present the bitchin' innertube wallet to solve all your wallety needs.
Step 1: Assemble Your Materials
1. Innertube. I recommend a mountain bike tube rated in the 2.1 to 2.6 inch range. Patches are optional but add a nice touch. You will need about 6-8 inches of innertube.
2. Thin steel sheet. I had a spot welded piece of 22 gauge sheet steel sitting around that was magnetic, and easily cut with my available snips. Rust is optional but gives street cred.
3. Metal snips. My brother-in-law has been borrowing my legitimate tin snips for about six months so I had to use my "super scissors" (pictured) which put the hurt on them. You should use real snips designed for steel. Since I had about 25 minutes to complete the project, I had to make due.
4. A magnet. I used a rare earth magnet from a broken 2GB Caviar HDD that I had sitting around. You will need something stronger than a fridge magnet, but the steel sheets will shield your credit cards from the super strong rare earth magnet for the most part.
5. Rubber cement. I used a bicycle tube patch kit to glue closed the assembled wallet.
6. Lastly you need some kind of file or sandpaper to smooth the steel pieces you will cut.
Step 2: Cut the Metal Backer
Once the metal is rough cut out of the thin steel, you should round the corners with your snips, and then smooth out the edges with a file and some emery cloth. I know I didn't include the file and emery cloth in the materials, but if you don't have something to smooth the edges sitting around your workshop then forget joining the smelly rubber wallet club.
Step 3: Start the Assembly
Once you jam this metal piece in, you will want to get the magnet ready for insertion. To do this, cut another piece of thin steel that is approximately the same size as the magnet. Make it square with round corners for ease of insertion. Smooth to edges and corners as previous. See pic.
Once you have the smaller steel sheet cut and smoothed, place your magnet on it and eyeball where you will need to cut the innertube to allow the magnet clip to hold your hard-earned cash. Leave a little (about 1/2" ) of extra innertube so that you can glue the innertube closed so that the magnet doesn't espace. See pics.
Once you have the innertube cut, then clean and scuff the opposing surfaces of the tube as it you were patching a tire. Use the scuffing tool provided in a typical bicycle patch kit. Insert the magnet on the metal piece. The key is to have the metal piece you inserted into the main body of the wallet to interact directly with the metal piece you cut for the magnet. The metal backing of the magnet is typically non-magnetic, so you will want the two steel pieces to touch, through the innertube to hold your cash while minimizing the magnetic field present at your credit cards. You will know if you have too much magnetic field at your cards if they stop working. You have been warned. I personally have had no problems.