Do you know "Sashigane"?

Do you know "Sashigane"?

Jan 29 2020

Do you know "Sashigane"?
It is a traditional ruler used by Japanese carpenters.
This right-angle ruler is a tool used not only for measuring dimensions but also for accurately marking the slope of a roof and for various purposes. Those technologies are called "Sashigane-jyutu (technique)".
Also, depending on the type of "Sashigane", there are many variations, such as the old Japanese unit "Sun", the circumference can be measured, and so on.
The most characteristic is that there are scales on the front and back.
"Sashigane" in the image is the simplest, and when the ruler is turned over, the scale is written from the right side in the opposite direction to the normal.
That's why I use it often when I take pictures to record the dimensions of the knife. This is because the knife can be measured from the right when the knife is placed face up on the engraved surface.
I really wanted to explain "Sashigane-jyutu", but gave up because it was too complicated.