Charcoal fence, or baskets .
Porceloin coated steel is very heat & corrosion resistant, but hot coals in contact with the walls can cause micocracks leading to rust through.
When indirect cooking a basket or fence just to keep the coals from direct contact will extend the life of the cooker.
Two options weber makes charcoal baskets for kettles ,well made & inexpensive,but for smokes don't hold a lot of fuel.
I made a charcoal fence for a friend from light expanded metal ( like at HD or Lowes)
Cut a 4 in high segment from 24 in sheet, attach the ends with bailing wire , & shape into half circle to fit on kettle charcoal grate.
The light stuff cuts with tin snips & is fairly easy to shape, for a fence the heavier guage isn't needed & besides its much harder to work with.