Fitting system including base seat surface and leg support segments. The seat surface segment is displaceable in relation to the base segment, and the leg support segment is pivotable between a storage position and a use position, and wherein the relative positions of the seat surface and leg support segments with respect to the base segment are forcibly coupled to each other. The seat surface segment is connected to the base segment by a first bracket. The leg support segment is pivotable about a pivot axis fixed in position with respect to the base and leg support segments. The leg support segment is connected to the seat surface segment by a second bracket pivotable about a pivot axis on the leg support and seat surface segment sides.