Propane soldering torches with closed flames are used for safely soldering roof flashings and sheet metal. These irons need tanks and hoses, but burn hotter under all kinds of conditions. They're a must if you're going to solder in colder and windier conditions. The propane units use tanks that you can buy almost anywhere, typically used for barbecues. These units do make some noise and fumes. The Sievert Propane Irons are a little bigger than the Express Propane Irons and have bigger copper bits so they're nice for flat-lock work. The Express, being a little smaller, fits into tighter spaces better (such as inside gutters). You can't go wrong with either of them.