Step 9 : create the skylight rafters (a new body)

Note: Actually the roof of the dormer has four rafters, but the objective of this tutorial being to show how to use exterior pilot parameters, they will be built here as a single piece.
It's up to you to detail them if you feel the need.

In this new body, create a reference plane 900mm from the XZ plane
(facade plan of the dormer).

In a new sketch created in this plane and after making the "SketchOpening" 
master sketch visible, create a carbon copy of this master sketch
and then adapt it as needed.

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.