Outer Flap

The outer flap is a technical term in carton packaging structure, referring to the longer flap among the two pairs at the top or bottom of a corrugated carton that is located on the outermost layer and folded first. In a standard regular slotted container (RSC), inner and outer flaps appear in pairs; the outer flap is usually slightly longer than the inner flap and, when folded, covers the inner flap to close and protect the contents. It is mainly used in packaging design, carton procurement, logistics transportation, and packaging clauses in foreign trade contracts. Note: the length of the outer flap must be calculated precisely; if too long, it will make sealing difficult or cause the carton to bulge, while if too short, it cannot effectively cover the inner flap and sealing performance will be affected. Board thickness and stacking strength must also be considered. The difference from the inner flap is that the inner flap is folded into the box first, and the outer flap is then folded over it; together they form the locking structure of the box lid. Foreign trade practitioners should clearly specify the outer flap dimensions, material, and sealing method when communicating packaging specifications with customers to avoid cargo damage or claims caused by non-compliant packaging.