What type of profile do you need to create when using the Roof by Extrusion command?

To create a roof using the Roof by Extrusion command in Revit, you need to use a specific type of profile that guides the shape of the roof being generated. The correct option involves selecting a closed profile, which allows for the definition of the roof's edges and overall form.

In this case, using an open profile, such as a rectangular cross-section, means that the profile would not fully enclose an area necessary for creating a roof. A closed profile is essential because it provides the boundary needed for the extrusion, ensuring that the roof maintains a consistent shape along the defined path.

While a triangular cross-section might be suitable in certain scenarios, it still needs to be closed for the Roof by Extrusion command. Circular cross-sections are typically related to cylindrical roofs and won't suffice for traditional flat or sloped roofs created through extrusion. Therefore, a closed profile in a more common shape, like rectangular, visually conveys that it's meant for roof structures and meets the requirements for the extrusion to produce a valid roof element.