An apparatus for the production of a jacket for a recording disk from a foldable blank, comprising a stationary receiving surface for one half of the blank and a further surface, pivotable essentially through an angle of 180.degree., for bending over the other half of the blank; a sheet-like spacer member which can be positioned over the stationary receiving surface, and one of whose edges, serving as a folding blade, is allocated to the swing point of the two said surfaces; and means for heating the fold area of the blank.