two of {TAIL ~ said plates} are insertable in {HEAD ~ opposite directions} into said entrances, respectively, in said flat sleeve 
two of { TAIL ~ said plates } are insertable in { HEAD ~ opposite directions } into said entrances , respectively , in said flat sleeve
OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH