Chirality is the fancy word for handedness. It's important in organic chemistry
(I think it was only one chirality of thalidomide was mutagenic --http://www.uh.edu/engines/epi604.htm), in molecules
and also in scissors, for instance, or driving an American car in England (apart from the narrowness of the roads).
We spinners talk about it quite often, when we discuss S-spun and Z-spun yarn.
Some people have 'mixed brain dominance'(notably Charlie Brown, although as Lucy asked, "Have you ruled out stupidity?"). They may be somewhat left-handed, or not, or be ambisinistral (when I dance) and they are much worse than usual at right and left. MUCH worse. Like, I say, "Turn left," to my mother, and she turns --> because she thinks it's left. Since I also think it's that way, we work all right. Most other people end up pointing for us, or shouting "The OTHER left!" or something more expletive.
It's a very mild but very real learning disability, since most people seem to do "Right" and 'Left" as if they were clearer than 'right' and 'wrong,' which we all agree -- well, we don't but we do admit there are circumstances. People act like Right and Left were as real as North but North is the same way whichever person you are on the train, for instance, whether you face toward or away from the engine.
I can do clockwise and counterclockwise all right. I know I write with my right hand, I can't remember what handedness I spin (I mean, cf Too Much Wools's discussion of spinning, how can you tell? Both hands are important). I know I used to be near-sighted in my right eye and far-sighted in my left, which was quite handy.
Chirality is about mirror images. Not having any facility at this, I am bad at relatively simple tasks, like piecing quilts that go
l-l-l-. I have to keep looking and even if I piece two together -l, if I want to put them with another two I have keep checking I have make sure they are not upside down, say. I don't think I can show it in ASCII. "Inside out" I know they are not, because there are seams, and I know two verticals or two horizontals don't touch. And you don't get a star of one color among four blocks. This leaves out most of the wrong ways around, you would think.
Doing a Rail Fence Quilt for me is probably different that it would be for most of you. I am poor Soren K, Fear and Trembling all the way. I remember you have to make the centers of pairs match, and if you can keep certain seams in line with one another you can make quite convincing paths (please don't measure the widths of the individual strips. They vary. Square is an ideal, right? Platonic, practically. And random error is my friend, at least I hope so. We see each other quite often).
Rail Fence, in my world, works best if you make up chunks of blocks, rather than lines, and sew them together. So it seemed quite reasonable to make half of the center lengthwise, and then the other half. Within those 36 blocks, there are nine lines of four rows. I unsewed quite a lot of them because I would find elves had come in the night and put chunks in upside down.
I was sewing the last eight onto the second half and held them against the first half. Perfectly obvious they were upside down, one removes them. Then it slowly dawned on me that each half was perfect. But not the same. Chirality strikes again. I have to unpick ALL THIRTY-BLEEDING-SIX squares, the ones I have spent quite large parts of the last two days sewing together.