The term “gao ya xian” in Chinese means literally a high-voltage line which is connected with the danger of electric shock by contact or proximity. But in daily conversation, it is often used to refer to top prohibitions, rules that one should never break, because it will prove to be as lethal as touching the high-tension wire.

　　“高压线”这三个字在字面上指的是高输压电线，触碰或者接近这种高压线都有被电击的危险。不过，在日常生活中，“高压线”经常被用来指代那些绝对不能触犯的规章制度，因为一旦触犯，其后果就可能会像触碰了高压线一样有致命的危险。

　　For example:

　　When you are in a new company, the first thing you should do is to determine the top prohibitions there, something you should never touch.

　　刚到新公司的时候，你首先要做的就是摸清那里的高压线在哪儿，有些事情是绝对不能碰的。