On a family meeting I started talking about the Moebius band. I actually made one out of paper to make it visual, but they kept looking at me like I’m stupid and insisted, that this piece of paper obviously had two sides.
Friggin uneducated assholes made me look like an idiot. I really wanted to shoot them in the face, one after another.

“Note that this is an “abstract” gluing in the sense that trying to realize this in three dimensions results in a self-intersecting Klein bottle. The Klein bottle, proper, does not self-intersect. Nonetheless, there is a way to visualize the Klein bottle as being contained in four dimensions.”

You can’t actually build a real Klein bottle in three dimensions. The model is just for visualizing it. Also for storing al-kee-hol.

A while back a fairly kind person sent me one of these in beer-mug shape. It’s still a Klein bottle, too, and believe me it’s a hell of a lot easier to understand them when you’ve had a few drinks from one.