Parts Required:

1. Old Hub Axle or M10x1.0 Thread Bar
2. Old Quick Release Skewer
3. 2x M10x1.0 Lock Nut
4. 20x20mm Mild Steel Box Section
5. 2x O-rings
6. 1x M4 Screw (Not really necessary)

Tools Required:

1. Hack Saw
2. Drill
3. Assorted Drill Bits
4. Step Drill Bit (14mm)
5. M4 Tap (if using M4 screw)

If you are having shifting issues it could be due to a bent derailleur hanger. This tool allows you to determine if your hanger is straight and realign it if necessary. Your rear wheel does not have to be true, just use the valve stem as a datum.

Notes:
Adjustment Screw is from https://www.thingiverse.com/thing:1959208/#files (Scaling to 98% maybe required)

The additional hole at the bottom of the tool isn't required, i just poorly drilled it the first time.