typical examples of how a heat deformable member 4 is formed to conform to a body portion such as the back of a wearer in fig1 a and 10b there are shown typical material configurations from which the heat deformable member 4 may be fabricated the heat deformable members 4 are preferably of a plastic heat deformable material 20 with fabric layers 21 22 on opposite sides thereof as disclosed in said u s pat no 3 906 943 one of the fabric layers 21 22 which are securely adhered to the plastic layer 14 is preferably of an insulating material to prevent heat from the heated up insert from being uncomfortably transmitted to the body of the wearer when the insert is being formed to conform to the body contour of the wearer as shown in fig1 b the plastic material 14 may be provided with a foam layer 23 to replace one of the fabric layers in use the foam layer 23 is directed toward the body of the wearer to provide additional cushioning to provide impact absorption characteristics to the device and to generally make the device more comfortable in normal use the foam layer 23 also acts as the insulating layer when.