The allen key bolt goes on the reverse side, threads in throught back plate and the lock washer and nut goes on the front face of the cam gear. When I saw the threaded back plate I also wondered to myself why a nut is even needed? and why didnt they just put the allen head bolt on the front face like most other camgears. But I suppose its much easier to tighten and undo a 10mm nut from the front than an allen head bolt what can strip internally. An a 10mm nut is easier to tell if it loosens up too I guess.