{HEAD ~ One side wall} of the housing defines {TAIL ~ an opening} through which the tubing reel may be slidably removed 
defines
{ HEAD ~ One side wall } of the housing defines { TAIL ~ an opening } through which the tubing reel may be slidably removed
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH