Tool designed,

for precise alignment front wheel with respect to the handlebar. Got the idea from some commercial tools available on the market.
The laser angle is adjustable to compensate different models of stem. 

Before use check the laser alignment of the tool by putting it on it's side on a flat surface and check if the laser is pointing at the same height eg on a wall when the tool is flipped to the other side. You can adjust the height by rotating the laser and fixate it again.

update:

• added an adapter for a smaller Stem diameter (for version 0.2) 
• increased depth of the V-slot for larger range of Stem diameters (version 0.3).
• Adjustable tilt with 2x M3 inserts and changed Laser type to 12mm USB Cross (link below, Version 0.4).

Check also my other designs: https://www.printables.com/social/201278-hans/models

Parts:

• Laser
• Laser 12mm USB Cross
• M3x10mm
• M3x20mm (2x)