They are called kegaki. Scribing gauge produced by Matsui. One of the best layout tools I own. Metric or shaku only.
http://www.matsui-seimitsu.co.jp/scriber_gauge.html
They are made to high quality standard and I certainly recommend them.
Your comment really makes me wonder wether you speak out of experience?
I am sorry if I might have discouraged someone or gave the impression that a kanna is too difficult to use or setup. This is certainly not the case and I can only encourage anyone to use them. They are not only fun but...
One could easily write a whole book just about kanna it's use and setup. That aside there are quite a few good resources about how and why. Two books come to my mind the really famous one by Toshio Odate and also Des King's book about shoji has a really good chapter on kanna setup.
Chris Hall...
Trying to add a modest point of view as it was thought to me by my teacher Kaneko-san.
"..your stone and bevel should be perfectly flat..." (I might add that perfect would be within a visible tolerance which you can see with the naked eye).
It is not always considered 'good practice' but...
Are the sides angled inwards towards the bottom? I find this a prerequisite for all hardware if you hope to install them recessed and completely seamless. It doesn't need to be much just the tiniest bit but it does allow to insert them and compress the sides of the corresponding hole a little...
If you are looking for high quality nomi for an affordable price the either Kikuhiromaru or Ouchi are top. With high quality I mean long lasting edge and ease of sharpening.
They are worth every penny if you compare this to their performance.
I wonder where you got this specific information from? I would love to know more about the subject, especialy if you have any info on the active particals in natural stones.