**Geometric construction** is the system of proportional rules by which the elements of a flag — stripes, crosses, triangles, charges — are sized and positioned, expressed as fractions of the hoist. A well-specified geometric construction allows the flag to be reproduced at any scale without distortion. National authorities ordinarily publish a construction sheet to fix these proportions.
**Example**: The geometric construction of the Union Flag specifies the widths of the crosses of St George, St Andrew and St Patrick, and the offsets that make the counterchanged saltires recognisable.
**See also**: [construction-sheet](/glossary/construction-sheet/), [proportions](/glossary/proportions/), [ratio](/glossary/ratio/), [fimbriation](/glossary/fimbriation/)