With the rod knock thrice at the iron door of the castle, and it will spring open.

At a loss for a moment, he lifted his hand to knock thrice on the corrugated door.

Before going into the sitting-room the grandmother knocked thrice at the door.

Carmen went up to the door, whistled softly, and knocked thrice.

Knock thrice at the latter, and it will be opened.

The older man gave the younger a shrewd glance, and knocked thrice at the door.

Leaving it, we came to a door in the wall on which my companion knocked thrice.

He sped faster now, and presently came to two great doors, on which he knocked thrice.

I knocked thrice, and received no reply.

He knocked thrice and entered.

Even that was withdrawn; for the guide, having knocked thrice at a door, blew out the candle, and retreated down-stairs.

I knocked once, I knocked twice, I knocked thrice, and then the door opened and I enjoyed a fresh sensation.

The "little maid" was still lingering, but she added mysteriously, "She'll be knocking thrice at her mother's door to-morrow."