I don't know anything about the book in question, but I assumed it was because of the way the hook at the end of tape measures has a little play to it. If it's a poorly made tape measure that doesn't account for this properly, you get slightly different measurements by hooking around something versus pushing it against a surface.

(See point #5: https://www.ustape.com/hidden-features-of-measuring-tape/)

[–] Peppycito@sh.itjust.works 4 points 7 months ago (2 children)

That wiggle is an 1/8". 12ths of an inch aren't really a thing.

[–] Buddahriffic@lemmy.world 2 points 7 months ago (1 children)

Oh right, fractions of an inch are usually expressed in fractions of powers of two. SI humour went right over my head because I'm used to seeing weird fractions involved in those measurements.

[–] Peppycito@sh.itjust.works 2 points 7 months ago (1 children)

Feet are divided by 12 but inches are divided by 8. And a yard is a foot times 3.

It makes way more sense when you use it, but trying to explain it does make it sound crazy.

[–] Buddahriffic@lemmy.world 1 points 7 months ago

I thought it was powers of two because it's not hard to find the halfway point between two other points, so you find the 1/2 mark, then the 1/4 mark, then 1/8, 16, 32, depending on how much precision you need. Then, at some point the unit changes again to mils or something like that.

After doing some digging in to this, I was thinking of the thou or mil, which is a thousandth of an inch. There's also another one that I hadn't heard of: the line, which is apparently equal to... 1/12 of an inch. Lol full circle.

[–] frezik@midwest.social 1 points 7 months ago (1 children)

If it's a poorly made tape measure to begin with, doesn't really matter. Could easily end up with 1/12" off.

[–] Peppycito@sh.itjust.works 1 points 7 months ago

If it's really bad it might even be 2/7ths!

[–] Pulptastic@midwest.social 1 points 7 months ago

Don't forget the 1/2" drywall, 3.5" studs, 1/2" foam thing, and siding.