a sleeve 21 provided with internal screw thread not shown and a fixing element 23 provided with a through hole 24 sides 25 and an upper side 26 comparable to the fixing element 13 of fig2 the fixing device 20 can be fixed as such to a weld stud not shown in fig3 a 3 b but forming part of the fixing device provided with external screw thread as will be explained in more detail yet with reference to fig6 fig4 is a perspective top plan view of a clamping element 30 comparable to the clamping element 3 of fig1 the clamping element 30 may be made of plastic material or of a n at least slightly elastic metal the clamping element 30 comprises a beam shaped central element 31 which is provided with keyhole shaped recesses 31 at the short ends thereof arms of an anchoring member not shown in fig4 having a circular cross section can be accommodated in the circular part 33 of the keyhole shaped recesses 32 the arms not shown can be guided to the circular parts 33 via guide surfaces 34 of the keyhole shaped recesses 32 the keyhole shaped recess 32 is narrowed at the location of the transition between the guide surfaces 34 and the circular parts 33 of the recesses when the clamping element 30 is placed partially surrounding an anchoring element the guide surfaces 34 are pushed apart by the arms of the anchoring element after passing the guide surfaces an arm of an anchoring element is clamped down in the circular recess 33 in that the guide surfaces will eventually resiliently return to their original position a comparable situation is shown in fig1 two wings 35 on either side of the beam.