Product review (4 stars): Effective tool - instructions not so much
This tool works pretty much as described once I adapted the procedure in the instructions for my particular duct run. My fixed duct is 26 ft long with 3 elbows. I found it easiest to disconnect the elbow right before exiting my crawl space and running the tool back towards the dryer ( for safety I also disconnected the flex duct to prevent potential damage to the dryer. For long runs, I recommend adding one section at a time, run drill scrubbing back and forth, before adding the next section. This takes longer, but prevents the fiberglass rods from torgue twisting. I needed 7 sections in all. Amazon sells the 4 rod extension kit. I also found that my drill would not turn more than 2 rods with the clutch set below half as recommended. Set on maximum clutch, I had no trouble turning 21 ft of rods. I have not tried this tool to unplug a gutter downspout, but see no reason why it shouldn't work quite well.