Method for rolling up a sheet, and holder for a rolled-up sheet

An assembly comprising:

• a rolled-up sheet with no creases, the rolled up sheet comprising:
• a first and second pair of opposite edges, two edge regions along the first pair of opposite edges, and a centre region enclosed by the second pair of opposite edges and the two edge regions, wherein the edge regions touch each other near the first pair of opposite edges and form a flat end region, the curved centre region of the rolled-up sheet being rolled up around a longitudinal axis to form a rolled-up end region and
• a holder, comprising a first support surface, a bearing part and a clamping part, wherein the rolled-up sheet is at least partly enclosed in the holder with the first support surface supporting the flat end region of the rolled-up sheet, the bearing part supporting at least one of a first pair of opposite edges of the rolled-up sheet,
• wherein the clamping part is pivotably attached with respect to the first support surface, and is configured to pivot between the holding position and an open position, in which the rolled-up sheet cannot be clamped between the clamping part and the first support surface, and
• wherein the clamping part, in the holding position, leaves an opening, which extends across a clamp width Bk and a parallel to a surface width Bv of the first support surface, between the clamping parting and the first support surface, wherein the opening has a sufficient opening height Ho for rolling up the curved centre region of the sheet in a direction of the flat end region through the opening and into a rolled-up sheet clamped in the holder, and wherein clamp width Bk is less than the surface width Bv.