Abstract: The frame of the motor vehicle carries a vertical rail defining an elongated track for a plastic slide which carries a first pivotable lever serving as a means for releasably coupling the slide to the rail. A pivot member which secures the first lever to the slide carries a deflector for the shoulder belt of the occupant restraint system, and the first lever has a tooth which is biased against one of two sidewalls of the rail to enter into one of a row of sockets in the one sidewall. A second lever or a wheel is provided to extract the tooth from a selected socket and to thus enable the slide to move along the track to a different position in which the tooth is aligned with a different socket. The first lever is centered between the two sidewalls which flank the track for the slide. The central portion of the first lever resembles or constitutes a disc with two convex surfaces which are closely adjacent the respective sidewalls and have centers of curvature on or close the pivot axis of the first lever.