Our fixed glazed windows are installed as part of a zinc standing seam roofing project that Top Drawer Zinc are contracted to install. Windows are not sold individually to contractors or end users. View More Windows are only installed by Top Drawer Zinc Ltd. The windows are technically fixed roof lights as they are non-opening. They can be used below 15º and as low as 8º which in my experience is the average greatest pitch usually available for new extensions on the projects that I work on.