According to Genesis, God closed the door of Noah’s Ark.
Genesis 7:16 says that Noah and the animals entered the ark, and that the LORD shut Noah in. The wording makes the closing of the door an explicit divine action rather than an act attributed to Noah or one of his sons.
This detail appears immediately before the Flood waters rise. It emphasizes that Noah’s household and the animals were secured inside after boarding. The verse also summarizes the animal arrivals by saying that creatures came in male and female pairs, according to the categories described in the surrounding passage.
The narrative gives the Ark a single door, but it does not describe the door’s engineering, dimensions, hinges, or locking mechanism. Later paintings and films often add such details imaginatively. The specific biblical claim is narrower: after those commanded to enter were inside, God shut the door.