I’m in the midst of shaping my first board and using John Carper’s Shaping 101 video as my primary source of info/technique (and Swaylocks of course!). I bought a long strip of aluminum carpet tracking at Home Depot for a batten to make my template. It looked exactly like what JC was using in the video. It didn’t flex as much as I would have liked but I got by with it. Later I went back to see if they had anything else better and found the exact same thing only in a narrower width and slightly lighter gauge. It is 7/8” wide versus 1 and 3/8” and is super flexible, you can practically bend it into a circle and it came in a 12 foot long piece. I’ll be using it next time. Just tell the sales person you’re looking for long strips of aluminum to merge carpet to a wooden or tile floor and they’ll know what you’re talking about.