Intersect
Extract curves resulting from the intersection of the sketch plane with selected parts or surfaces.
Create Intersection Curves
- 
                On the Sketch ribbon, select the
                        Intersect tool.

 - On the toolbar, select Parts to choose parts to intersect with the sketch plane, or select Surfaces to choose surfaces to intersect with the sketch plane.
 - 
                Select part(s) or surface(s) that intersect with the sketch plane to create
                    intersection curves.
                The intersection curves appear as a dotted red line or curve, and can interact with your new sketch.
 - Right-click and mouse through the check mark to exit, or double-right-click.