said {HEAD ~ mounting fixtures} are capable of inverting {TAIL ~ a mounting direction} of said device relative to said first user, 
are capable of inverting
said { HEAD ~ mounting fixtures } are capable of inverting { TAIL ~ a mounting direction } of said device relative to said first user ,
OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH