Then I'm gonna draw two lines straight down.

然后画两条垂线。

And if it's bending towards this normal line...

如果它的折射光线靠近这条垂线。

Above what Harry assumed was the title of the story (being unable to read runes, he could not be sure) , there was a picture of what looked like a triangular eye, its pupil crossed with a vertical line.

哈利认为那故事的题目（不会读古代魔文，因此并不能确定），这一张看起来像三角形眼睛的图片，瞳孔处有一道垂线。

And what the carpenter did, because he was quite a clever chap, is he went to stand on that spiral staircase and he let his plumb line down and he drew it back up.

而木匠做的， 因为相当聪明的人，就站那螺旋楼梯上， 放下的铅垂线， 然后又收了回来。

For example, it is known that if we draw perpendiculars to the sides of a triangle from the opposite angles, all three perpendiculars meet in a point.

例如，众所周知，如果我们从相反的角度向三角形的边绘制垂线，则所有三垂线都会交于一点。

Sivert especially had a genius for knocking in nails, but Eleseus was better at handling a plumb-line.

Sivert 尤其擅长敲钉子， 但 Eleseus 更擅长处理铅垂线。

Drake would have learned to feel his way along the coast with his lead line.

德雷克应该学会了用铅垂线沿海岸摸索前进。