A precisely straight rule to check the condition of the sole of the dai. The cut out is so that you can check the sole with the blade set in position = protruding. It is impossible to use a Japanese plane properly without this equipment.

Each rule is checked and adjusted to precision by craftsmen. Usual rules are not straight enough to check the sole.

Good for checking the flat of the sharpening stones for precision sharpening. Again usual rules are not flat enough to check the stone's surface.

Highest Quality
Matsui Precision MFG (Co.)