Please don't hurt me! Before going to gas some years ago, I didn't know about chimneys for charcoal cooking. When I got my WSM a couple months ago, I just grabbed a cheap chimney from my local grocery store because that's where I was getting my charcoal(didn't like it, now use the walmart brand of briquettes) and it was there and I hadn't looked at a Weber chimney to see any differences. Now that I've used it a bit and recently ditched the gasser and have my 18.5 Budlight OTS, I've noticed a few differences between the Weber and my off brand. But haven't purchased the Weber chimney yet. The most obvious is size(and yes, I know there are two sizes for the Weber), no explanation there. then there is the bottom design, the Weber is a an angled coil/concentric circles whereas mine is a flat piece of metal w/holes drilled(guessing the Weber would allow for better airflow and quicker heating..etc).
Now to my question. My current chimney has the barrel, a heat shield and a handle. I've noticed the Webers have a a pivoting arm. What is that for/do?