A thumb break strap or flap or {HEAD ~ other type} of retainer may be used in {TAIL ~ this embodiment} 
A thumb break strap or flap or { HEAD ~ other type } of retainer may be used in { TAIL ~ this embodiment }
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL