The Record

Jun Maekawa

1958–
Cited on every fold as: Maekawa, J. — mountain–valley count

Observed that at any vertex which folds flat, the mountains and the valleys differ by exactly two. It is a counting rule, not a measuring one — and it is the second gate every fold on this site must pass.

Source: Maekawa's theorem: |M − V| = 2 at every flat-foldable vertex. Earlier statement of the same count: S. Murata, 1966.

The hands behind the rules