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