Abstract: A ventilating device which includes at least one ventilating section for running down the roof of a building or structure which is capable of being opened and closed to enable the structure to be ventilated, a support arm connected to the ventilating section to permit it to be moved into and out of a ventilating position and an actuating arm capable of movement relative to the support arm, so as to move the support arm and the ventilating section into and out of a ventilating position. The invention permits the actuating arm to be maintained in a predetermined position to hold the support arm and ventilating section in a position in which the ventilating section is in a substantially non-ventilating position.