To draw a line (on paper, a map, etc.). Figuratively, to mark a boundary or make a distinction clear.
重要な箇所に赤で線を引いておいた。
I drew a red line under the important parts.
会議で意見の線を引くのは難しい。
It's hard to draw a clear line in opinions during a meeting.
地図に境界線を引く必要がある。
We need to draw boundary lines on the map.