The Skylight tool is used to add a skylight to a roof. A skylight is a window installed directly into the roof to bring natural light into a room below. For example, you might add a skylight to brighten a hallway, bathroom, or attic space without adding a regular wall window.

To use the Skylight tool, go to the Roof tab in the main toolbar and select it. Then click on the roof surface where you want the skylight to be placed. Once added, you can adjust its width, height, and trim settings in the Properties panel to fit your design. After placement, you can customize the glass type and materials and check how it looks in the 3D view to make sure it allows the right amount of light into your space.