Working with Purchased and Multipurpose Parts - Autodesk Inventor 2010: No Experience Required - page 282

Now, let's place some mounting holes in the part.
6. Create a new sketch on the work plane you created by starting the
Create 2D Sketch tool and selecting Work Plane 1 in the Browser.
7. Use the View Face tool (PgUp key) to get a view of the machined faces.
8. Use the Point tool to create a sketch point in the middle of each of the
two faces. See Figure 6.26.
FIGURE 6.25 The trimmed part
FIGURE 6.26 Inserting points into the sketch