also be possible to provide more than two projections 4 with a corresponding plurality of cutouts 40 the blank p leaves the punching tool and can be supplied to a further device in which the flat tube shape is produced the flat tube 1 is produced with a minimized welding gap 16 in a narrow side 12 subsequently the projections 4 can be bent down by means of a bending tool the bending angle may therefore be about 35 degrees to 45 degrees fig5 the flat tube with the bent down projections 4 is transported to a further device in some embodiments the aforementioned punch s or press has been expanded into a more complex sheet metal reshaping installation b framed in fig1 from which the reshaped flat tubes 1 with the bent down projections 4 issue cyclically the sheet metal reshaping installation b contains at least one tool w for producing the flat tube shape from the blank p in other words in the preferred embodiment the projections 4 are bent down as early as during the course of the production of the flat tube shape that is to say before the welding of the longitudinal seam complex sheet metal reshaping installations of this type are known per se that is to say apart from the device v integrated therein for bending over the projections 4 during the bending over of the projections 4 the flat tube 1 may still be clamped in the tool w in this state the.