Geometry
Glue flap
A glue flap is an extra strip of a packaging blank that bonds to another panel to form a seam.
What it means in packaging
Its width, position and surface treatment must work with the adhesive and the folder-gluer. It is part of the structure, but often not a visible artwork panel once assembled. A narrower flap does not automatically mean a better sheet yield.
A practical example
A tuck carton body closes when the narrow side flap is glued behind the opposite body panel.
What to check
Keep the agreed glue area compatible with the adhesive; ask whether ink, varnish or laminate must be excluded.