c, are side views and a plan view, respectively, of the legs of the first embodiment; [0020]FIGS. 5a and 5 b are a top view and a side cut-away view, respectively, of the non-magnetic cover of the first embodiment; [0021]FIGS. 6a and 6 b are a top view and a side cut-away view, respectively, of the tubular stem of the first embodiment; [0022]FIG. 7 is a cross-sectional view of one female section a