Method of producing an outer sheet that includes barrier flaps, and an outer sheet produced in accordance therewith

A method of producing an elongate sheet of material having side edges, the sheet includes barrier flaps that extend along the side-edges of said sheet in spaced relationship with said side-edges and which barrier flaps project up from a plane of said sheet, the elongate sheet having at least one first elongate web of material, at least two second webs of material, and at least two third webs of material, the method comprising:

• placing along each side edge of the first elongate web of material one of the second elongate webs of material whose width is smaller than a width of the first web, such that the respective outer side-edges of the second webs will lie edge-to-edge with the side-edges of the first web;
• placing along each side edge of the first elongate web one of the third elongate webs whose width is smaller than the width of the first web, said third webs being placed on the respective second webs such that the outer side-edges of respective third webs will lie edge-to-edge with the side-edges of the first web and said second webs;
• joining the first, second and third webs together with a join that extends along each of the outer side-edges of the webs;
• and
• swinging the third webs laterally outwards about their join lines through an angle of 180°, and stretching the elongate sheet comprising the mutually joined first, second and third webs laterally, wherewith the second webs are lifted up from the plane of the first and third webs.