In the preferred embodiment, the second side wall 38 straddles and is contact with {HEAD ~ the upper surface} 50 and a second side surface 53 of {TAIL ~ the support beam} 31 and the first side wall 47 is in contact with the outer edges of the support beam 31 
In the preferred embodiment , the second side wall 38 straddles and is contact with { HEAD ~ the upper surface } 50 and a second side surface 53 of { TAIL ~ the support beam } 31 and the first side wall 47 is in contact with the outer edges of the support beam 31
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH