If the bottom ply includes one wall, {HEAD ~ the wall} can be positioned either between the top ply inner and outer walls, or inside of {TAIL ~ the top ply inner wall} 
positioned inside of
If the bottom ply includes one wall , { HEAD ~ the wall } can be positioned either between the top ply inner and outer walls , or inside of { TAIL ~ the top ply inner wall }
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH REL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL