Abstract: This invention relates to a device for fixing fasteners to the flaps of corrugated cardboard boxes for sealing the flaps. With the fastener placed across the adjoining edges of at least two flaps, piercing nails in the form of a cow horn and attached to a pair of turnable pieces on the fastener are driven into the flaps by the device. The device is characterized in that two reciprocally movable sliders (12, 13) move to drive a cutting blade (17), causing the blade to separate a fastener from other fasteners, and subsequently drive pivotal members (29a, 29b) to depress the turnable pieces on the fastener, driving the piercing nails into the flaps. Fasteners can be fixed in place easily and reliably.