Thus, the wheels 23 are faced with {HEAD ~ the slope} 311, and {TAIL ~ the propped surfaces} 312, 313 
Thus , the wheels 23 are faced with { HEAD ~ the slope } 311 , and { TAIL ~ the propped surfaces } 312 , 313
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH