What a coincidence. I use a 10cm ruler.
I have twelve inches but don't use it as a rule.
oh yes lets all measure our little weenies and brag about it now.
perhaps boliver uses a micrometer.
There is no real definition of distance. But at a certain point, everyone agreed that a straight piece of metal of a certain size would be the standard of distance.
Ah! That is why the builder in the house in front was carrying that vaccum machine attached to a laser! it was his very modern tape measure!