This is simply a bit driver attached to a D-Ring carabiner. The bit holder slides around the ring allowing you get great leverage and get at hard to reach fasteners. It's a simple but versatile tool for your pocket, glove box or tool box. It's easy to make and you'll wonder how you ever got along without it.

Step 1: What You Need

You'll need to get the following materials
D-Ring Carabiner (3-5 inch carabiners work best, bigger is better. They don't need to be "load bearing")
Hex Nut (large enough to slip into the carabiner and go all the way around. The flat sides need to be big enough to drill a 1/4in hole into)
Short Magnetic Bit Driver (The kind you'd use in a power drill)

You'll need the following tools
Hammer
1/4in Drill Bit
Center Punch
Square or Triangle needle file (must fit into a 1/4in hole)
J-B Weld (or what ever you prefer)
Drill or Drill Press (Not Pictured)

Step 2: Preparing the Nut

You will need to drill a hole in the side of the nut to accept the magnet bit holder. Use a center punch to start a pilot hole directly into the center of one side of the nut.
Drill a 1/4in hole into the nut.
Once the hole is drilled you will need to file the hole into a hexagon that matches the bit holder.
Be patient, this takes a while. You want the hole to be as tight as possible. You should nee to use the hammer to persuade the bit holder into place.

Step 3: Attaching the Bit Holder

Now you need to attach the bit holder to the nut.
First you may need to grind down the bit holder until it fits in the center of the carabiner.
Use the hammer to persuade the bit holder into the hole you filed into the nut. Be careful as the nut may not be very thick on the sides and may split if forced to hard.
Also you don't want to got too far through into the nut or you won't be able to slip it onto the carabiner. If you go too far through just use a file to expand the threaded hole.
Once installed use some J-B Weld around the base to hold the bit holder in place.

Step 4: Assemble and Enjoy

After the J-B Weld cures you slip the bit holder onto the carabiner and add some bits. To carry the bits you can use a small pouch that clips to the carabiner or find a bit holder keyring like in the pictured. (I got mine at Ace Hardware)