Home Improvement

I picked up a couple steel-coated fireboard heat shields for my wood stove(s) and need to install them against the wall, with a minimum air gap behind of 21mm / 7/8".

I'm looking for suggestions on what to use for standoffs/mounts. I considered some galvanized steel u-channel sign posts, but not sure if they are ok at high temps, and the shop selling them couldn't verify it either. It would be convenient since I could use the existing holes to bolt them to the wall. Would these be ok? Do you have any better suggestions? I'm not sure if my 18V Ryobi drill can make it through steel pipes or whatever else so please consider that in your suggestion, or tell me how I could pull it off.