If clean, simple joinery is required, welded joints may be appropriate. Three very different versions exist: electrically welded, the more traditional fire welded and gas welded.
Another option is to use discretely hidden dowels, pins, or other mechanical fasteners. We try to avoid using using visible nuts and bolts where ever possible, unless they are part of the design.
Alternatively, more creative joinery can be used as an expressive design feature in its own right. Blacksmiths have a large repertoire of techniques they can call on; a selection of these is discussed below.