An arrangement for fixing a side plate to a radiator includes a panel and a corrugated convector plate. The side plate bridges over a distance between the front side of the panel and the rear side of the convector plate at the end walls of the radiator. A positioning member is disposed between a section of the convector plate and an adjacent edge of the side plate. In one preferred embodiment, the positioning member has a spacer of a thickness which corresponds to a minimum desired distance between the edge of the side plate and the convector plate. Further, the positioning member has an alignment portion which includes an accommodation space for a part of the edge of the side plate. The positioning member also has an engagement portion which includes a recess for a section of the convector plate.