flat lead

例句：

1. 1. The artist carefully drew a flat lead on the paper.
   艺术家小心地在纸上画了一条平直的铅线。
2. 2.The engineer used a flat lead to measure the distance between two points.
   工程师使用一条平直的铅线来测量两点之间的距离。
3. 3.The painter used a flat lead to create a smooth and even stroke.
   画家使用一条平直的铅线来创造平滑且均匀的笔触。