I am in the process of plumbing the brake system for my '37 Buick. I've done my share of brake work but I'm not an expert. Usually if I needed to replace a line I'd buy a premade piece and install it and if I needed a longer run I'd buy two pieces that made up the length and joined them with the proper brake line union. On the Buick I decided I want to run solid pieces of brake line from point to point. This is the first time I've ever made my own double flared ends. Before starting I searched the HAMB to find out how the "experts" did it. I found some very helpful posts. I started by borrowing a double flaring kit from Advance Auto, the place I bought my line from. I attempted about 10-15 times to do a double flare and I wasn't successful at any. The groves in the clamp were pretty smooth and I didn't think they were gripping the tubing properly. I borrowed a kit from a friend and my luck changed. After doing about 5 crappy flares I hit on how to do them. I still didn't do them 100% but I got decent. I even had my 17 year old son doing them, he did about as good as me. After I did a successful flare I cleaned it off and inspected it under a magnifying glass for any flaws or cracks. I did this with all of the "good" flares. Of the flares I thought looked good from just casually looking at them about 25% had minor flaws I found under the magnifying glass and I rejected them. I don't think I was being too picky, I just wanted to make sure they were as close to perfect as possible. I got to thinking, how many people who do their own lines ever really closely look at their finished product before threading them on and tightening them up? Even the pros, do they closely scrutinize their flares before installing them? I think this is a very important part and it wouldn't take much of a flaw in the system for a catastrophic result.