The height setting device has a setting element (14) which can be locked in various positions along a guide rail (1). The entire height setter or parts of it can be moved against the pressure of at least one deformable element (20) towards the relevant side beam (5). The deformable element (20) may be a compression spring. The setting element may be in the form of a shell passing at least partly round the guide rail. The side (17) of the setting element facing the interior of the vehicle may have a threaded bush for fixing the fitting.
