The USE and INTERSECTION tools allows you to bring geometry (Lines and points) from other features and place them on the current sketch. Those lines can then be used to create other geometry.
The USE tool tool is located in the middle of the sketching toolbar.
Using Brophy Tutorial 0 -Sample part, create a sketch on the bottom of the part and practice using the USE tool to project the hole edges to the new sketch. Review the Intersection Tool.
Add geometry from another section of a feature to your sketch.
Add geometry from a feature that intersects with the plane of your sketch to your sketch.