lead dot

例句：

1. 1. The lead dot marks the beginning of the line.
   铅点标记了线条的开始。
2. 2. The scientist used a lead dot to mark the spot where the experiment was conducted.
   科学家用一个铅点来标记实验进行的位置。
3. 3. The lead dot is a small, round object that can be easily seen in the dark.
   铅点是一个小圆形物体，在黑暗中很容易看到。