a joining element to be anchored in an object with the aid of a thermoplastic material and mechanical vibration comprises a sealing portion and a wall anchoring portion . the sealing portion is substantially cylindrical and has a smooth circumferential surface . the wall anchoring portion has a circumferential surface which comprises the thermoplastic material and energy directors . a cross section of the sealing portion envelops the cross section of the wall anchoring portion and is arranged adjoining to the latter on its proximal side . the joining element is anchored in an opening provided in the object wherein a cross section of the opening corresponds to the cross section of the sealing portion of the joining element such that the latter can be forced into a mouth of the opening resulting in a press fit . for anchoring the joining element in the opening , mechanical vibrations e . g . ultrasonic vibrations are coupled into the joining element and the latter is forced into the opening until at least a distal part of the sealing portion is positioned within the opening . thereby , the thermoplastic material of the circumferential surface of the wall anchoring portion is liquefied and pressed into the opening wall , wherein the sealing portion prevents the liquefied material to penetrate through the mouth and therefore the mouth remains clear cut , i . e . does not get blurred by the liquefied material .