The seat consists of a frame (3) which is connected by lugs to two sets of guide rails (1,2). The guide rails consist of outer guide tubes which are mounted via cages with balls on guide rods (81,82). The tubes are made frcm two halves with longitudinal flanges along their edges which are screwed or riveted together. The flanges increase the bending strength of the tubes. The ball cages are either in the form of sleeves with clearance holes for the balls or are pressed sheet metal cages for single rows of balls. The ball cages are held in position in the tube by pins which extend radially into the tubes.
