Abstract: Security proof shutter structure applicable to windows, doors, store or garage fronts, utilizing slats constructed of steel or the like. A special S-shaped spring linkage means is secured to respective ends of the slats. The lower hook of each linkage means being engaged with the upper hook of the adjacent linkage means to provide a rotatively operative linkage between adjacent slats without fixed attachment.The hooked linkage is well adapted to independently install or remove any one slat on site and to independently control by sliding the closing of the louvre spacing between adjacent slats or moving apart from each other. The louvre spacing between adjacent slats can be progressively closed or opened. The full lowering takes place with opened louvre spacing and by continued lowering the progressive closing of the louvre spacing between adjacent slats will take place. The winding around the upper roller takes place with fully opened louvre spacing.