Hi Deermaker!
So if I'm understanding, you're asking about cooking racks inside your vertical smoker build?
The most common and affordable material for the fabrication of cooking racks is mild carbon steel (it's what I use). Build a square or rectangular frame out of mild steel tubing or angle iron, then cover that with mild steel expanded metal, and you've got yourself a cooking grate. Then use angle iron along the sides of your cabinet to build a slide - or runner - for the cooking rack to slide into the cabinet.
While it's true that mild steel will rust when exposed to the elements, as long as you "season" the interior of your smoker - including all the cooking racks - and then cook in it regularly, it won't rust. The oils and fats inside the chamber will make a good rust inhibitor.
If cost isn't a factor, there are some who use stainless steel to build racks, but in addition to being more expensive, it's also harder to weld.
As far as spacing, in a vertical cook chamber, it's nice to have enough clearance between racks to accommodate larger cuts of meat like pork butts, whole chickens, etc. I try to allow for approx 5-7 inches of clearance if space allows.
I hope that answers what you were asking. If not, just give a little more info and I'll try again.
Good luck with the build!
Red
