26 may be pushed into the engaging portion of the retainer 10 for example as shown in fig8 d the first end of the heating element 26 may be inserted between the pressing portion 8 a and the supporting surface 16 of the retainer as set forth above the exemplary aspects of the invention may reduce an amount of linear translation of the heating element 26 between the pressing portion 8 a and the raised supporting surface 16 of the retainer 10 and also may reduce an amount of force needed to push the heating element 26 into the heating element retainer 10 as shown in fig9 the raised supporting surface 16 of the retainer 10 also may have a guide element such as a bump or protrusion 18 which may further guide the heating element 26 into the retainer 10 the protrusion 18 may be configured to fit between parts of the heating element 26 to guide the heating element 26 between the pressing portion 8 a and the supporting surface 16 for example in the exemplary embodiment shown in fig9 the heating element 26 may have a plurality of u shaped parts in this embodiment the heating element 26 may be inserted between the pressing portion 8 a and the supporting surface 16 such that the protrusion 18 interposes adjacent u shaped parts of the heating element 26 thereby guiding the heating element 26 between the pressing portion 8 a and the supporting surface 16 of the retainer 10 accordingly the exemplary aspects.