Preferably, {TAIL ~ each notch} 56 is flanked by {HEAD ~ two raised portions} 58 
Preferably , { TAIL ~ each notch } 56 is flanked by { HEAD ~ two raised portions } 58
OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH