This is Mike of Sheet Metal Workers Local 19 with ACG Roofing of Warminster, PA. He has been a sheet metal worker for over 30 years and is working on a job in Philadelphia, Pa. He is soldering the seams of a copper box gutter on this hospital. He is using is an Express self igniting iron and after sweating the solder into the joint once, he turns down the heat of the iron and stiches over it. This technique is also known as bridging and serves a purpose aesthetically as well as strengthening the joint. Some other key points he makes in the video are keeping the soldering tip clean of debris by using a wire brush as well as removing the flux / acid from the joint after use. Turning down the heat of the iron is also key and takes practice.