Re: chamferbox
Hi
If you go to create, then splines select rectangle. after you have created it, select the rectangle then go to the modifier, and in that you can change the corner radius to what you want.
Now go to the modifier list, press extrude, this will make the rectangle spline, 3 dimensional.
I hope this is of some help, if not please feel free to ask more.
Good luck, Tiff