a window assembly controls ventilation and prevents passage through the window opening . provides hardened steel horizontal bars spaced apart vertically a distance that prevents passage . the bars are welded to hardened steel frame members . the steel assembly is anchored in the wall by resistant anchoring elements . the bars may be secured in place by other means . glazed aluminum vents have top rails that enclose the bars and pivot upon them . aluminum frame members enclose the steel frame members and support operator means that rotate the vents on the bars to open and close the vents . the angle of opening may be limited to prevent the vent extending beyond the wall at walkways .