Abstract: A seat part is supported at the upper rails of rail arrangements which are arranged at both longitudinal sides of the seat and which comprise, in addition to an upper rail, a lower rail which receives the upper rail in a longitudinally displaceable manner. A locking device which can be disengaged from a row of teeth of each lower rail for the purpose of longitudinal displacement of the seat is arranged at the upper rails. The locking device has a release device which is coupled with toothed arms at swivelably supported locking levers, which toothed arms are spring-loaded in the locking direction. The release device has a two-part release lever formed of a swivelably supported actuating lever and a grip bar or actuating stirrup.