Abstract: An apparatus for adjusting the height of the upper fixing or guide fitting for the shoulder belt of a safety belt system, particularly in motor vehicles. The apparatus includes a guide rail mounted on part of the vehicle body, and has a guide slot and recesses in which at least one associated locking member engages. This locking member is mounted on a sliding member which carries the fixing or guide fitting and is capable of being locked in or released from the recesses via a handle. The locking member or locking members are symmetrical in construction with regard to their locking function, are mounted on the sliding member, and are operative in the guide rail, and especially are operative on both sides of the central longitudinal line of the guide rail. Moreover, the handle is designed, by a finger pressure construction, to be operated with substantially no force of the hand and arm, using one hand.