Fujimoto's method for marking one third in a square.
Left diagram. Mark diagonal, fold b
Bottom edge along diagonal and mark at A
Right diagram. Fold C to A and mark at M, this gives one third of top edge.
FUJIMOTO'S METHOD OF ESTIMATING A FIFTH AND TWO SEVENTHS OF A SQUARE
The methods below depend on the fact that the ratio of the
diagonal of a square to
Estimating one fifth.
Left diagram, mark diagonal and centre line. Right diagram, fold bottom edge to centre line and mark at M, this gives an approximate one fifth point.
Estimating two sevenths
Left diagram. Mark both diagonals. Right diagram. Put bottom edge along diagonal and mark S. This gives two sevenths up the diagonal (approx).