Editing Solids and Surfaces - Autodesk AutoCAD 2013 Practical 3D Drafting and Design - page 222

• Taper : This option allows us to taper faces. After selection, it prompts for
two points that define the taper axis and the taper angle. With positive
values, end section is reduced, while with negative values, end section is
increased:
• Delete : This option allows the deletion of faces. If AutoCAD knows how
to fill the space, faces will be deleted.