PURPOSE: To prevent a film from vertically tearing at the time of peeling off the film without dropping film locking ability at a temporary stopper by providing the temporary stopper for locking the film after cutting on a surface of a front plate covered by a folded lid piece and forming the stopper of two protrusions.

CONSTITUTION: A temporary stopper Q is placed from a position lower by 3 to 6mm from an upper end of a front plate 1 to a position up to a blade tip of a cutter K at the tip of a folded lid piece 5. The temporary stopper Q is shaped into a belt extending over an entire length of a box, wherein at three portions including the center lengthwise of the belt and both ends, cuts having a width of 1/2 to 3/4 of a belt width and a length corresponding no a lengthwise direction are provided, so that two resulting protrusions are formed with its top directed toward a bottom plane 2 of the box. Therefore at the time of cutting a film, a film locking effect can be securely exhibited an either of the temporary stopper Q lengthwise along the front plate 1. When the locked film is to be peeled off, the cuts positioned at three portions simplify the peeling.