Nuts and Bolts: ambigrams.

 Ambigrams are bits of writing that can be read in two different ways. This can be upside down as well as the right way up, or it can be from right to left as well as from left to right (as a mirror image).

The message you read can be the same in both directions, or it can be a different one.

Look at this image upside down, and you'll see that it's just the same as it is the right way up:

this image is By Basile Morin (Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=77857137). You can see it rotating on Wikipedia.

Ambigrams have been around for centuries. Here's one outside Hagia Sophia in Istambul:

The writing means wash your soul, not only your face. If you look, you can see that the N s are written backwards in the right hand part of the inscription, but it's still really clever, especially as this inscription is on a font.

Here's a more modern ambigram:

and one more:

that one's by Basile Morin, too.

What's the point of ambigrams? 

Well, they make you feel grateful to the creator, which in turn makes you think properly about the message, doesn't it?

But the sheer fun, cleverness and beauty are enough for me.

Word To Use Today: ambigram. This word was coined by the American cognitive scientist Douglas Hofstadter (no relation, as far as I know, to Leonard). The ambi- bit is Latin and means round, both, or on both sides; the -gram bit comes from Latin, too, from Greek, where gramma means letter.