When I was a boy
4/4 hardwood was 1" finished.
If you bought unfinished hardwood 4/4 you would get a board approx 1 1/4 thick.
Unfinished Softwood would be exactly 1" thick
Plywood was as thick as it said. 1/2" was 1/2" and 3/4" was 3/4"
And a 2x4 was 2"x4"
There was also dimensioned 2x4 (wall studs) and if I remember correctly they were 1 1/2 x 3 1/2 but could have been larger.
Then greed came on the scene and all kinds of explanations were invented to justify selling wood that didn't meet those specs. Like finished hardwood that measured any where from 11/16" on up to 1" as 4/4.
Selling unfinished 4/4 at anywhere from 7/8 on up
And plywood almost any thickness they can get away with.
Dimensioned 2x4 they are now slipping in 1 3/8 x 3 1/4
Try mounting and framing insided doors using that junk.
The width has even been more exciting.
However I'm blessed that I have lumber yards that still sell 2x4 unfinished at 2x4 and if you want you can even buy finished 2x4 that are 2x4.
And 4/4 finished hardwood that is 1" and 8/4 that is 2"
Unfinished 4/4 that is 1 1/8-1/4 and 8/4 that is 2 1/8-1/4
And they even have US plywood that is 1/2" 3/4" and 1"
They also sell the other stuff like 4/4 that is only 3/4 and 3/4 ply that is only 22/32 but they tell you what is what.
Thank God there are still some people with integrity.
And I almost forgot yes they let you sort the pile, however they expect it to be as neat and orderly when you leave as it was when you got there.