Internal liner for the bellows of a communication passage between two articulated vehicles, or parts of a vehicle

The inner wall cladding (1) includes a guide device (20) which has at least one guide arm attached to one of the wall elements (2, 3), running parallel to it and outer spacing from it. The guide arm movably supports the other wall element, so that the spacing between the first wall element and the guide arm is roughly equal to the thickness of the other wall element.