Abstract: A method and apparatus for repairing "hot spots" in a refractory lined wall, applicable especially to blast furnaces. A plurality of relatively closely spaced couplings are affixed in advance to a metal shell which overlies the refractory lining. When a hot spot is observed, a jig is installed successively on couplings overlying the hot spot and holes are drilled in the shell. The couplings accommodate a grouting machine which injects grouting material through the holes.