This is a guide/jig for drilling axle holes on a Pinewood Derby car. One side is at 2.5mm above the bottom and the other at 3.5mm so you can run 3 wheels touching if your rules allow. If not, just use the same side for all 4 holes. It's sized for 45mm width which worked great for me but you can scale the width slightly if needed to fit well.
The holes are a bit snug but you can drill them out easily.
To hold up to drilling, I used:
4 top/bottom layers
4-5 perimeters so you can drill out the holes if needed without destroying the internal structure