The invention relates to a device for partitioning the plastic parisons to give at least one semifinished open-surface product (6), where the device encompasses at least one means of partitioning (3) the plastic parison and one means of drive (2). The means of drive may be composed of one, but preferably of two, driven rolls. It has been found that use of the device of the invention can reduce or prevent the production of creasing and irregularity at the margins, i.e. at the cut edges, of the partitioned parisons, i.e. of the resultant semifinished sheets.