{HEAD ~ A cover} may be placed over {TAIL ~ the upper opening} to seal the main body against contamination, permitting storage of the material 
{ HEAD ~ A cover } may be placed over { TAIL ~ the upper opening } to seal the main body against contamination , permitting storage of the material
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH