Abstract: A fixing means for attachment to a base (1), e.g. to a level concrete roof, of a thermal lagging (3), e.g. a mineral wool mat, said fixing means consisting of a screw (2) or other nail binding to the base and a washer (4) located on top of the lagging, this washer carrying a tubular recess (5) partly penetrating into the lagging (3) and the bottom (6) of which is pierced by the screw and within which the head of the screw (2) resides. To the end of the tubular recess (5) has been connected by stays (7) a plug (8) fitting into a hole drilled in the base (1) and into which the screw (2) can be screwed.