Bricklayers and carpenters often use plumb lines.是什么意思？

Bricklayers and carpenters often use plumb lines.

瓦工和木工经常使用铅垂线.

bricklayers

n. 砖匠( bricklayer的名词复数 )；

例句
I'm just going to see that the bricklayers do the right thing.
我只不过是让砌砖工正确地干活.

and

conj. 和，与，而且，于是，然后，因此；

例句
I spend a lot on expensive jewelry and clothing...
我花很多钱购买昂贵的首饰和衣服。

carpenters

n. 木工，木匠( carpenter的名词复数 )；

例句
The estate carpenters were collected to dismantle the bed.
集领地的木匠们把那张床拆卸开了.

often

adv. 常常，经常，时常，再三；

例句
Genetic abnormalities are more often associated with faults in paternal DNA than in maternal DNA.
相对于母本DNA,基因畸变往往更多地与父本DNA上的缺陷相关。

use

n. 使用，使用权，功能；

例句
Abstain from sex or use condoms...
禁绝性事或使用安全套。

plumb

vt. 使垂直，用测铅测，探索；adj. 垂直的；adv. 恰恰，正，垂直地；vi. 做管道工；n. 铅锤，测锤；

例句
...learning to wire and plumb the house herself...
她学着自己给房子布线走管

lines

n. （演员的）台词，排( line的名词复数 )，线路，线条，方法；v. 排队( line的第三人称单数 )，用线标出，[棒球]（击球手）击出（平直球），给…安衬

例句
The battle lines were drawn after the government refused to budge from its final offer.
政府拒绝改变其最后条件之后，双方对立态势趋向明朗。