the tongue free end 38 in fig2 of the drawings the limiter structure 46 is shown centered on the tongue free end 38 longitudinal axis of revolution l but it can be located to either side of this axis as long as the location is within the middle third of the tongue free end 38 width or lateral extent e moving part 44 comprises the free end tip 42 cut into a flap 60 and locally deflected or bent to extend out of the predominant horizontal plane of the tongue 36 and generally normal thereto the movable part 44 is shaped as shown to be hook like with a relatively greater dimensioned head 58 and a reduced dimension neck 62 such that the head extends beyond the tongue free end 38 to intersect with the flexure frame first transverse portion 24 at locus 50 fig1 thereby to limit tongue 36 movement relative to the frame 22 the head 58 is shown as a single panel but may comprise multiple panels for added breadth of contact all to be within the central portion 52 fig1 of the tongue free end 38 with particular reference to fig3 and 4 the limiter structure movable part 44 is defined from the tongue free end tip 42 by making a cut 64 by etching or otherwise transversely of the tip and inward of the tongue free end 38 from e g the left hand edge 54 of the tongue free end 38 partway across the free end to the centrally located portion 52 of the free end to free the flap 60 of material from the tongue free end and leave an uncut.