The word louvre derives itself from the French word 'louvert'. The word refers to a shutter, blind, or window that has slats angled horizontally to allow the passage of air and light, which indecently, protects the room from direct sunlight, and rain.The passage of air into the interior space is increased when the openings between the slats are expanded.  Fully slatted doors are extensively used these days in furnace areas and laundry because they require the maximum ventilation. Many houses now use large louvred doors covering the maximum area of the wall for better ventilation.  These sliders have no hinged panels, hence occupying much less space than bi-fold shutters. They move smoothly along a metal track placed on the frame of the door.