Gliding, or sliding, windows are one of the most common window types found in American homes and are typically made of vinyl, fiberglass or a composite material. A single slider has one fixed panel and one panel that slides to the left or the right. A double slider has two operable panels, allowing more circulation to come through the window. Gliding windows are a great option for windows that face frequently trafficked areas because they don’t create a risk of people running into them.