Motor-vehicle seat unit

A seat unit can be screwed automatically to the body platform at four fixing points without the need to alter the seat setting during screwing and has a sufficiently rigid connection, in particular a sufficiently firm connection for seat belts which are fixed to the seat, to the body platform. The fixing regions are provided in the floor rail itself, in particular in each case at a distance from the free ends of the latter and in a profile region, extending essentially parallel to the body platform, of the floor rail. These regions are joined directly to a steep wall and, with the latter, in each case form a ramp, and are oriented such that they enclose as small an angle as possible with the floor rail, although this angle is kept sufficiently large that, in an installation setting of the seat unit, the axes of the holes extend in front of the front side of the seat and behind the rear side of the seat with a clearance of a few centimeters, which makes possible the use of a screwdriver unit.