PInewood derby axle guards

thingiverse

Super simple but convenient to keep your axles straight before the race. Quick to print. Use up to six M3 or M2 self tapping screws to secure to the underside of the car. #4 wood screws from the big box stores also work, but they're a little big. You can also use the screws to fine tune weight. It's dead simple to remove a screw at the weigh-in if you're a smidge over weight on the official scale.