According to Genesis, God instructed Noah to place a door in the side of the Ark.
Genesis 6:16 describes the Ark’s window and door as part of its construction. The passage says the door was to be placed in the side, while the text does not provide a detailed description of its hinges, dimensions, or locking mechanism. Genesis 7:16 later says that the LORD shut Noah in after the occupants entered.
This side-door detail is distinct from the Ark’s window. The window is associated with Noah’s later observation of the receding waters and the release of birds. Modern illustrations often add several openings or ramps, but those features are artistic reconstructions rather than specifications stated in Genesis.
The biblical account also mentions three decks and compartments. Together, these details present a large enclosed structure, but they do not amount to a complete engineering blueprint. “A door” is the direct answer to the construction instruction in Genesis 6:16.