In order to provide an easy means of holding the seat cushion and the back rest in a convertible rear seat arrangement in an estate car, a pivotable attachment part which is supported on components fixed to the vehicle is held by the force of a spring in an upwardly pointing, aligned position and the sleeve-shaped receptacle which is assigned to the seat cushion runs in a self-centring fashion into the upper end of the attachment part which ends in a conical holding pin.