You have a square cutout in which you need to constrain a round bolt.
You can can use a work axis to constrain to, or you can create a work surface from a sketch. In either case once you constrain to them, you can toggle the work geometry's visibility off.
In this video tutorial three methods are demonstrated.
- In the first a work point is created using the Loop Select option, then a work axis is created by selecting the work point and the face of the part.
- In the second method work point and axis are created in reverse order. A work axes is created, by creating an "in step" work point.
- In the third method a sketch is extruded as a surface.
Note: the actual video quality is better than this thumbnail preview appears.
The advantage of the work surface is that an insert constraint can be used at the assembly level, where as with the work axis a center line mate constraint and an additional constraint would be used.