There is described a method of creating a hinge in a body of expandable material, said body being substantially flat and having at least two planar regions connected by said hinge to facilitate folding of the planar regions about said hinge, comprising: expanding said expandable material to form said body; creating a region of excess expandable material in said body adjacent said hinge; and compressing said region of excess expandable material into the hinge of said body after the expandable material has fused to create a hinge having a concentrated volume of expanded material when compared to said at least two planar regions of said body.