'Tent door' in the Bible

And Jehovah appeared to him by the oaks of Mamre. And he sat at the tent-door in the heat of the day.

And he lifted up his eyes and saw, and behold, three men standing near him. And when he saw them, he ran to meet them from the tent-door, and bowed himself to the earth,

And he said, I will certainly return to thee at this time of the year, and behold, Sarah thy wife shall have a son. And Sarah was listening at the tent-door, which was behind him.