Was getting your parents to explain proportion and take scissors to a sheet not an option?

Interestingly, paper A4 wide (210mm?) by letter tall (11") is a thing in the TeX community.

Cutting paper is annoying to get straight without a paper cutter.

That a4 x 11" document size prints correctly on A4 or letter without scaling or cropping (the margins just change)

Squaring is at least pretty easy. Fold diagonally, fold where the edge crosses the paper, crease back-and-forth until it tears easily.

> take scissors to a sheet not an option?

My experience is that it is quite difficult to cut the sheet precisely enough if you just use a normal pair of scissors.

My technique was always 1) fold along the line you want to cut (makes it straight—maybe parallel if you have a good eye), 2) use your tongue to wet the creased edge, 3) open and re-fold along the same crease but for the opposite side (valley becomes mountain fold), 4) wet the creased edge again… It was easy enough to tear along the fold at that point.

Obviously just an anecdote.

The instructions were just there and I was certain it was the best plane ever if I just had the right paper format. And that they failed had nothing to do with my folding skills.

How I felt not having square origami paper as a kid.

(It's okay, I learned immediately how to rectify, uh, squarify, the situation.)

Yeah, it is easy to try to correct the situation as an adult afterwards. This was just an account of my feelings then.

And as I mentioned below - maybe exactly this was in the way from making the best paper plane ever, that could fly all the way to my neighbour? What did I know?

I sort of had the same issue, eventually went to a small local printing company. They had loads of scrap paper in all possible colours. They were very nice to me (I was a kid so that helps I guess), and I got a load of scrap paper for free. They even cut a lot of it in square size. This supply lasted me for many many years of folding pleasure.

That's super cool.

My mom was a secretary and so brought home typing paper for me.

When I was older, dumpster diving netted me 4 or 5 reams of typing paper (with a letterhead on one side—oh well).