The buffer element is disposed on {HEAD ~ the lateral wall}, and {TAIL ~ the lateral side} faces the lateral wall 
The buffer element is disposed on { HEAD ~ the lateral wall } , and { TAIL ~ the lateral side } faces the lateral wall
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH