rigid expanded aluminum one quarter inch thick strips that are formed in a sheet that have at least 50 open space or more between the strips to insure adequate light transmission the expanded aluminum can be done in distinctive spatial patterns i e diamond shaped elliptical shaped or other desired patterns for aesthetic purposes one expanded aluminum element 18 is sized around its perimeter and thickness to correspond to the perimeter of the polycarbonate sheet and to fit snugly within the frame members 12 and 12a as shown in fig1 along all sides the thickness of the expanded aluminum element is approximately one quarter inch in the preferred embodiment such that when placed against one side of the one quarter inch polycarbonate sheet and encompassed by the u shaped aluminum frame members which are one half inch across each u shaped inside channel of each frame member 12 and 12a both the polycarbonate sheet and the expanded aluminum are snugly fit tight into the frame members 12 and 12a to eliminate any type of vibration and to form a completely rigid independent storm shutter once the frame members and the polycarbonate sheet 16 and the expanded aluminum element 18 are firmly housed within the frame and the frame member is secured by fasteners or rivets the shutter 10 is ready for a plurality of different types of mountings on the exterior surface covering the window glass sliding doors or regular door such a mounting could be in sliding tracks side to side with a top and bottom u shaped track permanently affixed to the building above and below the window opening.