In Genesis, God tells Noah to make a door for the Ark’s entrance.
Genesis 6:16 includes the instruction to set a door in the side of the ark. The same verse also describes the ark’s three levels and a window or opening, giving a compact outline of its basic features. The door is the access point through which Noah, his family, and the animals enter.
Later in the narrative, Genesis says that the Lord shut Noah in after everyone had entered. This wording gives the door a narrative function as well as a practical one: it marks the transition from preparation to the Flood itself.
Translations can vary in how they render related architectural terms, especially the window and opening. The entrance, however, is conventionally translated as a door. It should not be confused with a gate, which is a common term for an entrance to a city or compound rather than the wording used for the ark in Genesis.