ive references Attention is drawn to the following places, which may be of interest for search: Friction stir welding of metals B23K 20/122 B29C 65/069{the welding tool cooperating with specially formed features of at least one of the parts to be joined, e.g. cooperating with holes or ribs of at least one of the parts to be joined}Definition statement This subgroup covers: Example 1, from JP502411