👉 Mullions, also known as double doors or double hung windows, are a type of window that has two glass panels placed on top of each other. These panels are typically made from clear glass and can be designed to open up to allow for more natural light into a room. Mullions are often used in homes with large windows because they provide an extra layer of protection against drafts and heat loss, as well as allowing more light to enter the room. They are also commonly found in commercial