A method of interconnecting individual longitudinally and identically transversely profiled plates, which includes in combination the steps of:
- longitudinally aligning end to end two longitudinally and identically transversely profiled plates to be interconnected so that their adjacent end faces at least nearly abut each other and their profiles are in longitudinal alignment with each other, applying a sheet metal piece profiled according to the profile of the plates to be interconnected to and across said plates over the area where said plates at least nearly abut each other, pressing said profiled sheet metal piece entirely and vertically into the corresponding profile of the plates to be interconnected transversely, and cementing said profiled sheet metal piece to said plates to be sealingly interconnected by fusion adhesive.