Abstract: A thin-walled can body having a terminal curled rim at an open end thereof, has this open end closed and sealed by a diaphragm which is first formed into a dished shape by a forming tool which then cuts the dished diaphragm from a web and places it on the open end of the body. The upturned edge portion of the diaphragm is subsequently pressed into adhesion between a heat-sealable layer of the diaphragm and the curled rim, the latter being hot, by a presser tool comprising a mount carrying a spring-loaded pad. The pad is resiliently deformable and applies controlled pressure directly on the diaphragm, thus effecting complete conformity of the latter to any irregularities of the curled rim.