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Dimensional lumber tape measure
(slrpnk.net)
I hope it’s not against the rules here, just saw this woodworking related xkcd that I enjoyed and thought it might be appreciated here:)
Just like 50x100's are usually more like 40x90's, or something even more insane - 39x86? Like I'm sorry, but the unit of measurement is NOT the problem, it's the centuries old "traditions" and "standards" to normalize dimensional lumber that are the problem.
At any rate, one should look at the names of boards as the ratio of their dimensions and leave the inches and mm out of it and it starts to make more sense.