Abstract: Rectangular blanks of laminated cardboard are converted into containers for foodstuffs or the like in an apparatus wherein the central portion of a blank is clamped between two coaxial tools one of which has a concave blank-contacting surface and the other of which has a complementary convex blank-contacting surface. The tools can enter the cavity of a matrix with edges at one end of the cavity serving to cooperate with edges bounding the surfaces of the two tools so as to define pronounced boundaries between the clamped portion and the adjacent outer portions of the blank. The tool with the concave front surface is caused to penetrate into the cavity and to push the other tool in front of it whereby the outer portions of the blank are converted into a pair of sidewalls with convex outer sides.