The back wall 39 is between the side walls and is generally at {HEAD ~ right angles} to {TAIL ~ each} of the side walls 47, 38 
The back wall 39 is between the side walls and is generally at { HEAD ~ right angles } to { TAIL ~ each } of the side walls 47 , 38
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH