A method of providing, by high-frequency welding of at least two construction parts (4,4′) containing polymer material weldable by high-frequency welding to an assembled large unit in which said construction parts are comprised, fastener means (1) on said unit, said fastener means being intended for anchoring and building up said unit. The fastener means (1) are made of an electrically conductive material, and a primer layer (2) is arranged on a surface of the fastener means (1) and is bonded by means of a first hardening. A material weldable by high-frequency welding is arranged on top of said primer layer and is bonded thereto by means of a second hardening for building up a connecting layer (3). The invention also relates to anchoring parts (5) for use for that purpose.