seam

Also called: seamed joint or welt

Standards

any surface connection joining two longitudinally oriented edges of duct surface material occurring between two joints

Source - AS 4254.2-2012: Ductwork for air-handling systems in buildings

HB50

joint for sheet-metal work, especially roofing, formed by folding over, singly or doubly, the two edges of two pieces of adjacent similar metal

The seam may be folded over flat, or left vertical as a ‘standing seam’.