Abstract: A bottom end closure of a carton to be heat- and pressure-sealed has four substantially rectangular panels (P6, P7-P9, P12 and P14-P16) of which the panels (P7-P9 and P14-P16) are divided by score lines (S3, S7 and S13, S17) into inner, triangular sub-panels (P8 and P15) and outer triangular sub-panels (P7, P9 and P14, P16) and have central lugs formed by pairs of small, rectangular sub-panels (P10, P11 and P17, P18) providing for gas-tightness at the apices (A1 and A2) in the sealed closure. Score lines (S4, S6 and S14, S16) provide lines of weakness across the whole widths of the roots of the central lugs, so that the lugs, when each folded upon itself, can adjust to the orientation of an outwardly folded panel (P13) during tucking of the panel (P13) inwards of the lugs, which are sandwiched between the panels (6 and P13). In the blank, the lugs and the panels (P6 and P13) are so dimensioned that they can interdigitate with the corresponding lugs and panels of the bottoms of a row of identical blanks.