Inserting a Skylight – Putting in a skylight is similar to putting in a dormer window. To place a skylight you need to create a skylight symbol. The way that you create the skylight is crucial to the way it inserts into the roof.
When you create a symbol for the skylight the insertion point of the 3D Symbol is used to relate the skylight to the face of the roof. The symbol cannot be a hybrid symbol. It must be 3D only. Create an extruded rectangle the size that you want, the actual size of the skylight that you want to create.