The main purpose of this post is to show off some gorgeous pictures of sumitsubo, the Japanese carpenters ink markers, equivalent to European chalk lines.
I’ll also give a brief overview of the measurement system and the different way carpenters mark out their timbers.
Whilst Japan went metric in 1924 carpenters the world over tend to hang on to old units and so in Japan they still use the shaku as the base measurement. One shaku is 303mm or 11.93 inches so about a foot. This is subdivided into 10 and 10 again to give sun, bu, rim and mo. The carpenters square marked in sun looks close enough to an English square marked in inches to cause confusion. Houses have standard room sizes based on the size of tatami mats, though tatami mats vary slightly in size from region to region.
Now to marking out using the sumitsubo, European carpenters and joiners start marking timber by creating a single straight true face on their work and everything else is marked and measured in reference to that. Japanese do not work from faces they work from a centre line. So instead of snapping a line down the edge of a large log they snap an ink line down the centre and mark everything out from this. The sumitsubo is loaded with ink the line drawn out and pulled taught then snapped leaving a true line down an uneven surface. The joints at the end of each timber are then marked out equally either side of the centre line. I don’t have a photo of a centre line goin on but here is Hannes using a sumitsubo to snap a line for European style hewing.
And here is Ueki-san marking a joint for me. Rather than pencils they use a special marker made from bamboo dipped into the ink in the sumitsubo, it leaves a very thin crisp and waterproof line.
After a chouna the sumitsubo were the things I coveted most in Japan, they were simply beautiful objects, much loved, continually used and highly patinated. I will be making myself one but it will probably take years to get into the state of the old ones I loved.