What does “Shaku” means?

The shaku is a traditional unit of measure used in Japan (and other country in Asia) with a length approximately equal to 30.3cm or 11.93in. As with other measurements, it was originally derived from nature: the average length between nodes on bamboo.
The shaku may be divided into ten smaller units, known as  sun in Japanese. Ten shaku are equal to a jō in Japanese.

While Japanese law required official use of these units be discontinued in late 60’s, the shaku is still used in some fields in Japan, such as the traditional carpentry or swordsmithing.