Method for connecting parts relative to one another

The invention provides a method of connecting parts (1,2), the method comprising the steps of: providing a first part (1), the first part comprising an opening (1.1); providing a second part (2), the second part comprising thermoplastic material in a solid state; arranging the first part (1) and the second part (2) relative to one another, so that the second part (2) reaches into the opening (1.1), while a volume with an undercut (1.2) is defined in the opening(l.l); causing a mechanical pressure and mechanical energy to act on the second part (2) until at least a part of the thermoplastic material is caused to liquefy and to fill the volume (1.2); and causing the thermoplastic material to re-solidify, thereby anchoring the second part (2) in the first part (1).