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Fold paper in half. Both halves match exactly. That match has a name: symmetry.

Figure 1 — this track has two tests: fold it, or turn it.

What this track covers

Fold and match — what a fold line really has to do.
Not every line works — a line through the middle can still fail.
How many — a shape can have none, one, several. Or a never-ending count.
Symmetry around us — letters, leaves, and stone screens.
Turning — some shapes match without any fold line at all.
Complete it — half a picture. And the fold line gives you the rest.

This is Chapter 9 of your textbook, Symmetry. Fold a few things first. Read about it after.