Extruding
To extrude your 2D side of your car you must make sure
that every line is connected. Click on Levels list
and see how many lines that the program says is on the screen. If your
count is less than the computers you have a problem. You have to trace
over each line on a different level. You also have to make sure each
line is physically connected or you will get an error that says:

When you are ready to extrude click on
on the toolbar. It wil ask you how much it wants you to extrude. Enter
the height or width of your car. You should know this.Then select the
lines using the
command and select the color of your lines that you want to extrude.
Use the
key and
then use this to select your colors:

After you select the color click on the part of the arrow
that points to the direction you want to extrude your side to. Save
your work.