Step 10 : create the skylight ridge beam (a new body)

In this example, we are going to use a new type of link between geometries, the "shape binder".
 

In this new body, create a shape binder from the facade of the roof
of the skylight.

In a new sketch created from the shape binder, create the geometry
of the ridge section of the skylight.

Create an extrusion with a length equal to 600 mm.

In a new sketch created in the YZ plane, and from the "SketchRoof" 
master sketch, create geometry to cut out the end of the ridge according
to the plane of the main roof.

Create a pocket by symmetry through everything.