JELD-WEN Premium Atlantic Aluminum windows provide the reliability you are looking. Our aluminum windows include a unique performance feature - it's our patented silicone-injected corner key, which is created by injecting silicone into the corners for added strength. This feature also ensures the window is reliably weathertight. Double Hung windows feature an upper and lower sash that slide vertically past each other in a single frame. Tilt-in feature makes cleaning a snap even on the exterior of your windows.