Abstract: A method and an apparatus for facilitating the filling of insulation material into cavities (11) in hollow blocks (10). The apparatus comprises one or several drums (14,15), which are arranged over a conveying means moving blocks past the apparatus. Through the drums pre-cut pieces (12) of insulation material are passed toward the block. In each drum (14,15) a press plate (18) further is provided. Each drum is terminated downwardly by a laterally movable plate (16), which at each drum is provided with an opening (17) having a smaller width than the passageway. A reciprocating mechanism (22) is provided to move the press plate (18) to the rear wall (14) of the drum, so that the lowermost piece (12a) of insulation material is compressed, for example to half its thickness.