No sooner had I sat down than there was a loud knock on the door.

我刚坐下就有人大声敲门。

《牛津词典》

They knock on their neighbours' doors and shout "trick or treat".

他们敲了他们邻居家的门，然后喊着“不给糖就使坏”。

youdao

He got a nasty knock on the head.

他头部遭到重重一击。

《牛津词典》

Hey. (KNOCK ON DOOR) CHARLIE: Bella?

VOA: standard.other

It is no knock on him to say that he has 210 so far.

FORBES: The Business Mash

This will typically tend to have a knock on effect on lowering annuity rates.

BBC: Credit crunch benefits retirees

Buyers and investors alike agree that a one-time knock on earnings beats a drag that lasts for years.

FORBES: Digital Rules