铅垂线

例句：

1. 1. The engineer used a plumb line to measure the height of the wall.
   工程师使用铅垂线测量墙的高度。
2. 2. The painter carefully drew a vertical line on the canvas.
   画家小心地在画布上画了一条垂直线。
3. 3.The carpenter used a plumb line to ensure the roof was level.
   木匠使用铅垂线确保屋顶是水平的。