Abstract: A ventilator for slider type windows is provided, the ventilator having triangular end members and one or more bridging members extending therebetween. The ventilator is positionable between fixed and movable portions of the window and deflects incoming air upwardly or to the side. Each bridging member is provided with a pair of rib portions, each having a partially enclosed slot running the length thereof. Each end member has a slot adapted to receive the end face of a bridging member and has a pair of holes extending therethrough in alignment with the corresponding slots of the bridging member received therein. A screw extends through each hole and is threaded into the adjacent bridging member slot to secure the bridging member to the end member. The ventilator is particularly useful with combination storm and screen windows or doors. The ventilator can be packaged with all components flat and can be assembled and disassembled with ease.