two spacer blocks spaced from one another and each said {HEAD ~ block} attached to {TAIL ~ the forward surface} of said main receiving tube, 
attached to
two spacer blocks spaced from one another and each said { HEAD ~ block } attached to { TAIL ~ the forward surface } of said main receiving tube ,
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH