The retaining pawls are capable of being retained on {HEAD ~ the peripheral edges} of {TAIL ~ the retaining grooves} 
The retaining pawls are capable of being retained on { HEAD ~ the peripheral edges } of { TAIL ~ the retaining grooves }
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL