
While creating a part within an assembly, you are able to see and reference the other parts in the assembly. By default, when you reference geometry in another part, you get an associative relationship to that part. If the original part changes, the geometry that you created also changes to honor the association. In this tutorial, you use an option to reference the geometry without creating the associative reference. In situations where you are certain there will be no further design changes, not creating an associative relationship improves subsequent assembly recompute performance.
Format panel
Construction
to ensure that the line you project is “construction” geometry that will not be used for feature creation.
Draw panel
Project Geometry
, or right-click and select Project Geometry from the marking menu. 
Next, you create a simple, three-line sketch that represents the inside faces of the Contour Flange. It will create the basic shape of the guard.