by separating portions of a pair of joined sheets to form channels, e.g. by inflation (manufacture thereof B23P)

Full Title

Plate-like or laminated elements; Assemblies of plate-like or laminated elements (specially adapted for movement F28F5/00) > Elements constructed in the shape of a hollow panel, e.g. with channels > by separating portions of a pair of joined sheets to form channels, e.g. by inflation (manufacture thereof B23P)