EXTRUDE Command:

The EXTRUDE command allows you to create a solid object from circles, polygons, and objects, created from or converted to Polylines, that have "closed" paths.

To access the Extrude command you can:

type extrude or ext at a Command: prompt

OR

select Solids, and then Extrude, under the Draw Menu.

—Prompt: Current wire frame density: ISOLINES=4

Select objects: Click on the object you wish to extrude and press Enter.

—Prompt: Specify height of extrusion or [Path]: Type in value and press Enter

*NOTE: The height in an extrusion occurs along the Z axis; therefore, you must be aware of the orientation of the UCS.
You use a positive or negative value depending on the direction you want the extrusion to project.

—Prompt: Specify angle of taper for extrusion <0>: Type in an angle value if you wish to taper the extrusion or press Enter to select the default value of "0."

ITEMS THAT CAN BE EXTRUDED:

Example of "closed path" polyline: