The shelf as it stands now.
Cutting the steel pieces
I cut the square tubing using angle grinder and cleaned off the mill scale from the ends, where it’s going to be welded, using flap disc.
Welding the pieces together
I held the pieces together while welding using magnets.
Welding square tubing.
Both sides welded.
Drilling holes for the rivnuts.
Inserting rivnuts with a special rivnut tool.
I decided to add one cross piece at the bottom of the shelf, to meke it more sturdy.
Thinking of asking my nephew to make something similar. What did you paint the metal with to prevent oxidation and how did you do it?