Roof tiles are designed mainly to keep out rain, heat & cold and are traditionally made from locally available materials such as terracotta or slate. Modern materials such as concrete and plastic are also used and some clay tiles have a waterproof glaze. Roof tiles are 'hung' from the framework of a roof by fixing them with nails. A clay tile roof is a worthy long-term investment—long-lived, fireproof, resistant to damage from high wind, a thermal barrier that can buffer against extremes of temperature and, above all, an inescapably charming crown to the architectural styles that call for it. If the installer's workmanship is good and the weather congenial, it may even turn out to be economical.