xkcd #3138: Dimensional Lumber Tape Measure
Title text:
A person with two watches is never sure what time it is, especially if I got them one of the watches.
Transcript:
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Source: https://xkcd.com/3138/
If you sell me a 2" by 4" board, you cut it 2"+the width of the sawblade, just like the metric boards are sold.
Also is a saw really 1/2" wide? That's like 1.27cm, that's wild.
If you really really cannot sell a true 2"x4" at the price of a 1.5" x3.5", just keep the same price and call it what it is.
These boards are factory planed, not sawn.