But before he had a chance to place the call, someone knocked at his office door.

She moved away, and I knocked again at the door.

He knocked at the door, and the man told him to come in.

They just knocked at the door and said how would you care to take part?

But to make my mother happy, I knocked at their door.

A few minutes later someone knocked at the door again.

One of them went ahead and knocked at the door.

The man knocked at the side door of the building.

When I knocked at the door, he told me to come in.

She was about to answer when someone knocked at the door.