The bottom surface of the mounting surface structure attached to {HEAD ~ a top end} of {TAIL ~ the adjustable post mechanism} 
of
The bottom surface of the mounting surface structure attached to { HEAD ~ a top end } of { TAIL ~ the adjustable post mechanism }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL