introducing {HEAD ~ reinforcing material} to {TAIL ~ a cavity} at an angle of less than 90° with respect to said conduit 
to
introducing { HEAD ~ reinforcing material } to { TAIL ~ a cavity } at an angle of less than 90 ° with respect to said conduit
OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH