I need to try and come up with a jig to hold rebar together whilst it's welded. They have been trying to use slots cut into steel but the ends turn inside the hollow section at the slightest movement. I was thinking of making aluminium inserts that bolted in. I think holes strategically located in the bottom of the insert might hold the pieces in place. What I have been asked is to evaluate materials that reduce the spatter sticking to the jig. So I thought about using copper but not priced it up yet. Initially i Thought perhaps 40mm square bar might be an option. Welded into a square approx 600mm. But as always I looked at making it cheaper and easier to repair or replace. Which will inevitably lead to over engineering the solution. Lol Anyway guys take a look and See if I am close.