This invention concerns a heat-resistant assembly having a heat-resistant block conformed to the contours of boiler tubes and the surface of their connecting rib. The heat-resistant assembly has an arm which protrudes from the surface of the rib toward the heat-resistant block and which has a catch on the end. The block has an indentation in which the catch on the arm engages. The block can be hung on or removed from the tube assembly by means of the arms and indentations. The heat-resistant assembly is further distinguished by the fact that a space is created between the end of the arm and the indentation of the block. A fusible substance, which will melt when the temperature of the arm exceeds a given value, is placed in the space. The heat-resistant assembly is further distinguished by the fact that an indentation is formed in the block in which a heat-resistant sleeve is adhered to engage the arm. This arrangement makes it possible to manufacture the heat-resistant block using press molding.