a method and a device for fusing plastic profile bars , such as those comprising frames for windows or doors , includes a stop and a heat reflector for such a device . at least one of the profile bars already has inserted therein a gasket or seal . material from the profile bar or bars is displaced in the region of the at least one seal before or while the profile bars to be fused or welded are pressed against one another . the material from the profile bar or bars is displaced with at least one displacement element , which may be separate from or associated with the heat reflector .