An engagement occurs between {TAIL ~ the first and second elements} in {HEAD ~ the closed condition} of the abutment structure 
An engagement occurs between { TAIL ~ the first and second elements } in { HEAD ~ the closed condition } of the abutment structure
OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH