“走后门”字面意思是“enter by the back door”，比喻不是通过正当途径，而是通过内部关系谋取通融或利益(secure advantages through pull or influence)，带有贬义。

“开后门(open a back door)，则比喻当权者以权谋私，滥用职权为他人提供方便(abuse one's powers to secure advantages for others)。

例句：

她找工作走后门。

Someone is pulling strings to get a job for her.

这些年买名烟名酒用不着走后门了。

These years back-door dealings are not needed to buy cigarettes and wines of brand names.

他能走后门是因为他父亲是局长。

His father is the head of a bureau, so he got in through the back door.