This system is the simplest solution in technical and economic terms.
The shutter in the box cut at an angle of 45 degrees, is installed mainly on existing windows or facades. The size of the box depends on the whole height of the shutter and the type of armouring. This often determines the selection of the method of installation.
The stiff polyurethane foam, filling the profiles, is an additional thermal insulation.
The layer of air created between the lowered armour of the shutter and the window or door makes it difficult to exchange heat between the interior and external environments. It enables saving thermal energy necessary for the heating of the rooms, while on hot days it protects against their excessive heating.
There are versions with or without mosquito nets.