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