Abstract: Method and apparatus for detecting insecurely glued closure flaps on wrap-around paperboard cartons and for diverting defectively sealed cartons from the packaging line. A striking device in the form of an impact roller strikes the leading edge of each carton as it moves along a conveyor belt. Loose or insecure flaps opened by the impact are detected as the carton passes through a photocell station. Upon identification of an open flap condition a pivotal eject chute forming a part of the conveyor table is actuated downwardly to divert the rejected carton to a remote location for inspection and resealing or replacement.