I call it the Weber Flange Mod.
I suppose you can weld it to the drum if you wanted, but I make mine removable to use the drum lid for Turbo cooking or rotisserie rings.
Here it is on a closed drum to use a kettle lid. Leave @ 1/8" on your cut inside the rib and it will fit very tight with no need to weld-and it will keep the greasy buildup inside the drum and not all over the sides. (Don't ask how I know this!)
With an open drum for using either lid-Mostly for extra height, like Beer can chickens or Leg & Wing racks.
Works well with Rotisserie rings.
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