The knob 80 has {TAIL ~ an annular portion} 82 arranged for {HEAD ~ frictional engagement} with the exterior surfaces of the rear wall 66 on each side of the slot 76 
The knob 80 has { TAIL ~ an annular portion } 82 arranged for { HEAD ~ frictional engagement } with the exterior surfaces of the rear wall 66 on each side of the slot 76
OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH