I learned that the wheels on a Cub Scout Pinewood Derby car are a pain in the ass to get nailed in evenly.
Did you also learn that it's super annoying if you go over the maximum weight? You'll spend the first hour of the derby drilling holes into your car just to make it lighter so it actually qualifies for the race.
I learned that one last year. I have a shop scale now, and we're at 4.953 ounces. The max is 5 ounces.
I don't remember this being such a hassel when I was a scout. Maybe I should ask my dad.

)
Reminds me of the time I learned that my then 22-month-old son, who had started walking less than two months earlier, could open the doors of the built-in cupboard in the dining room and climb the shelves in order to reach the packets of crisps on the top shelf. Holy heart attack, Batman.