member 4 always remains in a position in which it is capable to engage from behind the holding projections 17 1 and 17 2 during positioning of the attachment system 1 and fixation of the screw 7 the undesirable rotation of the rear engagement member 4 relative to the mounting rail 3 being prevented by the transformation device 9 fig3 4 a 4 b show another embodiment of the attachment system according to the present invention the transformation device 31 includes an annular element 34 having a shape substantially similar to that of the washer for a screw the annular element 34 is formed of sheet metal or a plastic material the annular element 34 has two resilient servo components 32 and 33 provided thereon as shown in fig4 a and 4 b the transformation device 31 is located between the rotation torque transmitting means which is formed by a screw head 36 of a screw 35 and a stop 37 with the annular element 34 being glued on the stop 37 without a possibility of rotation relative thereto on a surface of the screw head 36 facing the stop 37 there are provided a plurality of indentation 38 in which the servo components 32 and 33 can engage as shows in fig4 b the servo.