A {TAIL ~ ledge} or mandible engaging support surface is defined between the upper tier and lower tier and terminates in {HEAD ~ an exterior opening} 
A { TAIL ~ ledge } or mandible engaging support surface is defined between the upper tier and lower tier and terminates in { HEAD ~ an exterior opening }
OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD