So Sticky, what are you using in the 22 as. Charcoal bank?
My thought is
1: keeps heat and smoke from charcoal directed upward to water pan for better indirect smoking, cooking.
2: Keep coals contained.
3: I've seen some use fire bricks, but mine locks into bottom charcoal grate so it can't tip over and seals to sides better.
Seems to work fine.
Pretty crude, but I made it while coals were getting ready.