I recently replaced all the downspouts in my house and found this tool very useful for cutting downspouts to the right length. To start cutting, I insert the bottom blade into the drain pipe just above the seam and cut in circles until I'm back on the other side of the seam. At this point I'm going to use straight scissors and cut through the seam. This tool actually cuts through the seam with no problem (which I tested), but I've heard that if you make the final seam with straight scissors, it reduces tool wear. By the way, I tried to cut the drain pipe with a saw and it was a mess with a lot of burrs and the vibration actually tore the seam on the gutter.