Abstract: A device for sealing a door or window casing by means of an insect-repellent gauze screen. The device comprises a rectangular insect-repellent gauze screen that is secured with one end to a roller rod, around which it can be wound and unwound, and with the other end to a pulling beam, which is provided with two handles. The roller rod is accommodated in a first frame section to be placed vertically. The pulling beam can be slid against a second frame section to be placed opposite the first frame section. The device further comprises a third and a fourth frame section, which possess a U-shaped guide section, in which an edge of the gauze screen is guided. The device comprises securing means so as to enable the fitting of the frame sections before the casing. The securing means are mounted on an inner wall of the casing, in particular on the transverse side of decorative parts present around the easing.