a hinge at the groove which allows tab 121 to pivot and slide up ramp 110 when a button is depressed when button 106 is depressed tab 121 will slide up ramp 110 and then up the body of button 106 until tab 121 enters notch 111 notch 111 may have a rectangular cross section and extend transversely entirely across upper barrel 107 of button 106 or may be a cavity formed in barrel 107 this form of notch is shown in fig3 in the latter case the material remaining on either side of the cavity provides a bearing surface which allows button 106 to move freely within holes 103 ramp 110 which extends transversely across upper barrel 107 of button 106 may have any convenient slope so long as tab 121 is caused to rotate about hinge point 122 spring means 123 surrounds upper barrel 107 and is compressed between cap 109 and surface 102 so that buttons 106 are urged upward at all times other forms of this invention are within the contemplation of the inventor for example button 106 could comprise several axially aligned cylinders this form of the button is shown in fig5 a shown therein upper barrel 107 has a larger.