which are secured in a radially offstanding manner on a shaping mandrel holder such as a wheel which is rotated in increments about a vertical axis the shaping mandrels are moved in succession to the various work stations of a bag making machine in the wrapper shaping station a table which comprises a die 12 matching the shaping mandrel 10 and two lateral table platforms 13 14 is movable up and down below a ready to use shaping mandrel 10 for receiving and presenting a flat blank 1 of packaging material between the die 12 and the two table platforms 13 14 two lateral folders 15 16 extend in the two planes of the lateral faces of the shaping mandrel 10 and are secured to a stem 17 that is movable up and down the height of the lateral folders 15 16 is such that in the upper position fig2 in which the lateral folders cover the two side walls of the shaping mandrel their upper edges protrude beyond the top of the shaping mandrel 10 preferably the protruding portion of the lateral folders 15 16 is somewhat higher than half the width of the top of the shaping mandrel 10 above the shaping mandrel 10 two folding slides 20 21 are pivotable on arms 22 23 onto the top of the shaping mandrel 10 to enable the two lateral.