thereof is provided with an angularly disposed recess 104 on opposite edges of the recess 104 are orienting means in the form of a pair of reference posts 106 with the forward edges thereof on the side facing aperture 100 falling on a plane passing through the center of the centrally disposed aperture 108 which is adapted to accept a fastening means such as a rivet 110 at the opposite end of the reed plate and overlying aperture 100 is the biasing bridge 112 which in this embodiment is integral with plate 90 bridge 112 includes an angularly disposed undersurface 114 having a low point 116 and a high point 118 the aperture 100 is opened into a t shape by the lateral extensions 120 which permit the integral two plate molding of the undersurface 114 it being recognized of course that the reed must be wider than the width of aperture 100 in order for it to be operative and hence the bridge must be wide enough to accept the reed the elongated flat metallic generally rectangular reed 130 as seen in fig1 and 15 includes a pair of struck up fingers 132 extending along the longitudinal edges of reed 130 toward an orienting shoulder 134 the shoulders 134 lie in a plane falling on the center point of a central aperture 136 midway along the extremity of reed 130 is a slot 138 which in the embodiment is cruciform in configuration the reed 132 is first threaded under the bridge 112 and then the shoulders.