window kind characterised by side hinges that allow it to open outward to either left or right. Some of them use alternative top or bottom hinging. One of the most popular types of windows in the UK given the versatility of possible designs. They are available in aluminum, timber, and UPVC options. They provide efficient natural ventilation and can be cleaned from both sides relatively easily. Thanks to the natural ventilation they provide through the hinging system, they are highly valued, especially in hotter areas.