square hole, round shaft mate

How can I mate a round shaft to a square hole. Sounds simple, ok,
please let me know. I sure would appreciate the help.
Thanks in advance.

 

Two "width" mades will do the trick.

 

As an alternative, I would draw a diagonal centerline acros the square
hole.
Then I would add a sketch-point at the midpoint of the centerline I
just drew.
After closing out of the sketch, I would go to insert>reference
geometry>axis, and make an axis with that sketch-point and the plane
that was used as the extrusion plane for the square

Then I would mate the shaft concntric to the new axis.

This is a little more robust if the width if the square hole or the
shaft changes during design changes
Ed

 

Big hammer.

HTH