A roller screen for shielding an opening in a wall or in an inclined roof surface

For shielding a window area (2) in a wall or an inclined roof surface (3) a roller screen is provided, e.g. an insect net (1), comprising a spring-biassed roller bar (9) at the upper edge of the opening (2) and a bottom bar (13) at the lower edge of a flexible screen web (1). The bottom bar (13) has guide members (17) slidable in guide rails (11, 12) having at the bottom a locking device for arresting the bottom bar (13). At either end of the bottom bar the guide members include a guide member (17) and a subjacent roll (18) pivotally journalled in the bottom bar (13) so that from a first position in which it is in axial alignment of the guide member, it may be swung to a locking position outside the path of motion of the guide member (17). The rolls (18) are functionally connected and biassed so that said first position and the locking position are stable switch-over positions. At the end of each guide rail (11, 12) a stop member (23) is mounted in which a lateral cutout (25) is formed at the bottom of a track (24) in axial alignment of the guide rail (11, 12) for receiving and retaining said roll (18) in the locking position.