A sack or bag is made of a collapsed, thermoplastic tubular film segment, which is provided preferably with side folds, by affixing head and foot welds and is provided on at least its head side with corner-partitioning corner welds. In order to be able to reseal such a sack after a partial quantity has been removed from its filling, the corners are provided in such a manner with cutouts, starting from the face-sided cutting edge, that the results are side strips, whose outer ends are provided with redetachable connecting means and that are designed so long that they can be folded in the outward direction by folding diagonally over the side edges of the sack or bag. After formation of a sack-sealing roll, the connecting means can be connected together for the purpose of fixing the roll in position.