What a bunch of know nothings we were as kids.
Look at all we missed out on by not understanding Z3 is stupid and Z4 is too hard but right in the middle is A-OK, I know my friends would have loved it had I interrupted our arguments about Empire Strikes Back with a long form monologue on Hard Star VO2 Intervals.
For me it was plywood placed over two and maybe three bricks with more bricks lined up beyond that to see how many we could jump.