In my past flash tutorials, I have received a number of emails saying that my tutorials are too long and boring. Well, that will change now. From now I will make tutorials short and straight to the point.
AutoCAD is a program used for 3D modelling, usually for landscapes and building plans etc. In this tutorial I will be teaching you how to extrude. I assume you know how to draw 2D and 3D objects, if not just play around with the tools (it's really easy, trust me). I will be using AutoCAD 2007, a slightly newer version but it shouldn't make too much of a difference.
Extruding:
The extruding tool in AutoCAD is used mainly for adjusting the height/depth of an object. In here, I have drawn a 2D rectangle; it may be hard to see:

Right now, the rectangle doesn't really *exist* and it cannot be rendered. But we will change that.
This is the extrude tool, it is located in the “3D make” control panel:

To extrude the 2D rectangle, I would click on the extrude tool and then click on the rectangle:

Once I have clicked on the rectangle, I would then press the ENTER key on the keyboard. Doing so would enable me to extrude the 2D rectangle, here I can physically adjust it myself using the mouse or I could input a value to extrude it to:

Once you are satisfied, click the mouse to make the changes or press enter if you inputted a value. Now you made a 2D rectangle into a 3D solid. To render, go to View > Render > Render.
This is what it would look like in render mode:

Note: Extruding is not just limited to rectangles.