It is a really neat system. Metal frames slide in and out of the middle of ceramic blocks. Because of rhomboid shape bigger on the bottom and smaller on the top, they don't fall out.
Nuts and bolts allow for adjustment and tightening. And the whole thing can be pulled apart and re-assembled.
Absolutely essential: to mark each piece exactly how it fits together - including which block is on the left and which on the right side of the arch, and which side faces in. And same for the metal frames.
That system worked on the bottom seven blocks on each side. Block 8 was too small to weld inside it, and even if I managed that, it would be impossible to reach the nuts & bolts
So the plan was for the top 7 blocks to be "threaded" on the metal frame and lowered onto the "legs" of the arch. Charlie ( on the photo below) welded larger square tube on the seventh frame, and smaller ( perfect size to slide into one another) onto the top arch frame.
After we made sure the metal bits all fit together, it was time to trial assemble the whole thing together.
Charlie was worried about ceramic blocks on the arch part, so he came up with the plan: