'Door' in the Bible

"To the messenger of the church in Philadelphia, write: "The one who is holy, who is true, who has the key of David, who opens a door that no one can shut, and who shuts a door that no one can open, "says this:

I know thy works: behold, I have set before thee an open door, and no man can shut it: for thou hast a little strength, and hast kept my word, and hast not denied my name.

Behold, I stand at the door, and knock: if any man hear my voice, and open the door, I will come in to him, and will sup with him, and he with me.

After this I looked, and, behold, a door was opened in heaven: and the first voice which I heard was as it were of a trumpet talking with me; which said, Come up hither, and I will shew thee things which must be hereafter.

Then I saw a door open in Heaven, and a white horse appeared. Its rider was named "Faithful and True" --being One who in righteousness acts as Judge, and makes war.

And the twelve doors were twelve pearls; every door was made of one pearl; and the street of the town was clear gold, as clear as glass.