I posted this to see what response I would get.
The responses are all great and very true.
However:
This question is a:
1 - Logical Puzzle (requiring one to think outside the obvious preverbal box)
or
2 - Some May Call a Brain Teaser.
"What's a lost skill that no one seems to remember..."
This is the key to this question.
There is no 'Lost Skill'.
If there was a lost skill then 'someone' would remember it; just like all the above answers to this question identifying lost skills; but someone (the poster) remembered one.
Don't worry, I fell for it also and came up with all the things the Alphabet Kids (Gen x, y, z, etc..) Don't Know and Never Will Never will Know or Learn.
Not to mention all the things (tools, shortcuts etc..) which are only known by someone who worked on a farm during the 1950 - 60s like I did on my Grandpa's farm.
Then last night I must have been dreaming about shxx and for some reason, I woke up, wide awake, at 3am and had the answer.
I don't think I fell back asleep until around 430am.
Please, don't bring up how the pyramids were made, it is obvious it was aliens who did it