noun
inked marking string; snap line
A carpenter's tool: a string coated with ink, pulled taut and snapped to leave a straight line on wood or other materials. Also used figuratively for a guideline or standard.
大工は墨縄を使って木材に直線を引いた。
The carpenter used an inked marking string to draw a straight line on the lumber.
このプロジェクトでは、安全基準を墨縄として守らなければならない。
In this project, we must follow the safety standards as our guideline.
Compound of 墨 (sumi, 'ink') and 縄 (nawa, 'rope, cord'). The word directly describes the tool: an ink-soaked cord.