To Extrude a Volume

Select the Extrude Mesh Volume tool ( Modeling > Mesh > Create > Extrude or Thicken Mesh > Extrude Mesh Volume ).
Select Extrude Volume.
Set the desired Direction.
Do one of the following:

Set Thickness.

or
Use AccuDraw to determine the thickness.
(Optional) Select Full Dynamics.
Click, use a selection block, or use a selection line to select the closed shape(s) or mesh element(s).
(Optional) If Thickness is not defined, define the direction and distance of the extrusion with AccuDraw. The cursor will automatically select the lowest point in the Z direction for the start of the extrusion.
Click to extrude a volume.
If Thickness is set, the extrusion previews.
(Optional) If Thickness is set, click again to extrude a volume.