each of wires strands 18a 18b and each strand is connected to one of conductors 22 when a soldered connection is used the heat applied during the soldering procedure melts the plastic sheet 23 overlying the conductor 22 and permits direct electrical contact between conductors 22 and the respective wire strands 18a 18b the overall height of the soldered connection is sufficiently small so that as shown in fig2 it lies entirely within the channel 24 rather than projecting below the bottom of the backing 14 in some circumstances it also may be desirable to strip the entire portions of the wire strands 18a 18b that underly the heating element 12 particularly if the dimensions of the wire or backing are such that the wire otherwise would project behind the plane of the back of backing 14 in early embodiments of the present invention strips 30 of dielectric tape dielectric tape type 34 premium 111 34 part no 4453 plymouth bishop insulating products were placed over channels 24 on both the top and bottom of cardboard backing 14 in currently preferred embodiments the strips 30 are omitted and instead sheets of organic plastic e g polyester film coated with a layer of a polyethylene hot melt adhesive are laminated over the entire top and bottom of the device in both types of embodiments the ends of each conductor 22 at each end of the heater which otherwise would be exposed when the element is cut from a longer roll of material may.