c f both the adjustment and the locking are carried out by means of the tool 200 which is described in greater detail below and is configured essentially tubular and comprises an exterior tube or a tubular shaft 211 and a rod 221 arranged rotationally therein arranged at the free end of the exterior tube 211 is the eccentric lever 212 the spigot or peg 215 of which is brought directly into engagement with the vertical slot 125 of the door side mounting plate 120 see fig1 d the free end of the tubular shaft 211 also encompasses the nut 131 which serves here as a rotary bearing or pivot point for the eccentric lever 212 the adjusting handle 210 is provided at the other end of the tubular shaft 211 in order to be able to rotate the eccentric lever 212 as illustrated in fig1 c the guide rail and the mounting plate 110 mounted thereon are initially situated in a starting position here for example at the right hand stop of the slot 121 which serves as a guide firstly the free end of the tool 200 which comprises the eccentric lever 212 is introduced through an assembly aperture provided in the vehicle door the end of the tubular shaft 211 is then fitted over the nut 131 of the screw connection in order to provide a pivot point for the eccentric lever 212 the.