Taper Face

1. Choose                     Modify, Solid Editing, Taper face
2. Choose                     a face(s) to taper. If you choose more than one face, hold the SHIFT key to deselect unwanted faces.
3. Press                        ENTER.
4. Specify                     the base point: pick the back left corner.
5. Specify                     another point along the axis of tapering: pick point
6. Specify                     the taper angle: 45

           solid                         validation started. solid validation completed.

Before Taper

After Taper