'Tent door' in the Bible

And Jehovah appeared to him in the plains of Mamre, and he sat at the tent door in the heat of the day.

And he lifted up his eyes and looked, and lo, three men stood by him. And when he saw them, he ran to meet them from the tent door, and bowed toward the ground.

And He said, I will certainly return to you according to the time of life, and lo, Sarah your wife shall have a son. And Sarah heard in the tent door which was behind Him.