mate together see fig1 25 in some embodiments upper portion 12 of adapter assembly 10 is circular although upper portion 12 can be any suitable shape upper portion 12 includes a front surface 18 and a back surface 20 fig4 in some embodiments a lip 19 extends from front surface 18 around the periphery of the front surface of upper portion 12 one or more cavities 22 are formed on front surface 18 of upper portion 12 the cavities being shaped and sized to receive one or more magnets 16 in the embodiment shown front surface 18 includes two cavities 22 the cavities 22 include a plurality of ribs 21 that help contain magnet 16 within cavity 22 once magnet 16 is pressed into cavity 22 in some embodiments front surface 18 also includes an indicator tab 24 which is explained in more detail below in some embodiments the cavities are of similar shape and size although alternative configurations can be used as shown in fig6 back surface 20 of upper portion 12 includes a left projection 26 and a left protrusion 28 which are spaced apart from one another to form first gap 30 back surface 20 of upper portion 12 also includes a right projection 32 and a right protrusion 34 which are spaced apart from one another to form second gap 36 left.