Abstract: An improvement in a bottom locking structure of a lay-flat type carbon of the type commonly used as a carton for beer bottles, the carton having divider panels formed from extensions of the bottom wall panels thereof. The improvement consisting of slot means opening through one of the divider panels at its hinged connection with respect to a side bottom wall panel and lug means projecting outwardly from the other side bottom panel, the lug means mating with the slot means as the carton moves to the erect configuration to provide a bottom wall interlock substantially in the plane of the bottom wall which serves to resist the return to the lay-flat configuration. In addition, the carton provides the further improvement wherein a side wall handle reinforcing panel is initially formed integrally with an end bottom wall panel. The end bottom wall panel is folded along its hinged connection with an end wall to locate the reinforcing panel to an intimate underlying relationship with respect to the end wall panel.