Flat Lock Metal Roofing by Walter Jowers A generation or two ago, sheet metal was used for just about all new installations of flat or nearly flat roofs. They were usually made of terneplate and commonly called "tin roofs." These roofs have a series of rectangular metal panels, or pans, which are bent to allow for flat, locked seams (thus the name flat-lock roof), and then malleted together by hand. The seams are laboriously hand-soldered. It's a type of roof that, with proper maintenance, can easily last a hundred years or more. Today, there are plenty of good roofing products that are easy to install on low-pitch roofs-metallized and rubber membranes that can be flame-melted into a continuous skin, and various synthetic