The end of the plug adjacent the threaded opening has {TAIL ~ a hexagonal square or circular exterior} for reception of {HEAD ~ a wrench} for connecting the plug to the flange opening 
The end of the plug adjacent the threaded opening has { TAIL ~ a hexagonal square or circular exterior } for reception of { HEAD ~ a wrench } for connecting the plug to the flange opening
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH