Abstract: A mandrel for opening a tube of flexible banding material wherein the tube is delivered in flat ribbon-like form with creased side edges is disclosed. The mandrel is in the form of a tetrahedron with two sets of surfaces which are in the form of isosceles triangles with each set of faces inclining towards one another to form a common base. A pair of relatively yieldable, sharp-edged wedging elements are disposed on each common base. Biasing means bias the wedging elements outwardly to limit positions at the ends of the common bases. Use of the mandrel to open a tube of flexible, heat-shrinkable banding material and creasing the material at points displaced 90.degree. from the initial creases is disclosed.