{TAIL ~ a passage} positioned at the second end of the housing and traversing from the top surface to {HEAD ~ the bottom surface} 
{ TAIL ~ a passage } positioned at the second end of the housing and traversing from the top surface to { HEAD ~ the bottom surface }
TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD