一いっ線せんを引ひく

expression, godan verb (-ku)

draw the line; set a boundary; make a clear distinction

Used both literally (drawing a physical line) and figuratively (setting a limit or distinguishing between things). Often implies a firm separation.

• 仕し事ごととプライベートには一いっ線せんを引ひくようにしている。

  I try to draw a line between work and private life.

• 彼かれはグラウンドに白しろい一いっ線せん