Here are a couple different views of the surface from Example 1 in the Lesson 24 notes.
For any of the following, click evaluate to render the image. It may take a few seconds to load. Once you see the image you may need to click again to be able to resize it by scrolling, or drag around to rotate the image. By right-clicking, you can reset the view to the first octant among other things.
Graph of the Mobius strip. This is the classical example of a one-sided surface.