Vertical bifold windows consist of two or more hinged framed window panels that fold on top of each other and move vertically. It is a similar system to guillotine window systems with some important differences. It can be called as a vertical bifold window, or it can also be called as a vertical bifold door system. Actually, it functions as a door more than a window on entrance level. A vertical bifold window can’t be applied at a full story height on the above-ground levels as it retracts only upwards.