Does the 18 in. x 24 in. Galvanized Steel Ventilating Access Door open inwards or outwards?

The 18 in. x 24 in. Galvanized Steel Ventilating Access Door is a 2-piece unit and the door is removable. It is not a hinged door.

The 18 in. x 24 in. Galvanized Steel Ventilating Access Door is a 2-piece unit and the door is removable. It is not a hinged door.