a face 72 of the retainer lies on top of the cam the retainer also has spaced apart arms 74 and a cut out portion 66 the entire retainer is preferably formed of cold rolled carbon steel and tee arms 74 may be forced apart the arms 74 have gripping portions 76 on their inner surfaces for gripping the groove 48 in the tenon 38 on the side of the axis of the tenon opposite the main body of the retainer 60 and cam 16 because of the configuration the retainer and cam cannot be easily removed i e they cannot be pulled off by hand the retainer also acts as a vibration damper due to its spring like construction for assembly in the factory the plug 12 shell 10 and switch 18 are assembled together in a known manner while the cam 16 retainer 60 and nut 32 as well as key 14 are shipped separately and unassembled to a customer for installation for installation the assembled shell 10 plug 12 and switch 18 are placed through an opening in the panel board from the front the mounting nut 32 is then threaded onto threads 30 of the shell to tighten the flange 22.