An apparatus for opening and folding the end of a flattened tubular sheet to define the rectangular base of a bag or sack to be made from the sheet comprises a table having a slot through which the flattened sheet projects, the projection being formed into a bag base by suckers locating the projection in a pre-opened condition and grippers which engage opposed margins of the projection, one of the grippers being fixed and the other being secured to a pivotable arm.
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