door the rail and the attenuation and retraction device are shown in cross section while the wheel cassette with included components are not shown in cross section as is shown the wheel 33 is urged against the rail and the pin 31 is in a relatively retracted position as is more clearly shown in the enlarged fig6 b the wing portion 51 of the pin is located above the tip of the ramp 45 thereby the wing portion 51 will follow the trajectory illustrated with a dotted arrow in fig6 b when reaching the ramp portion pulling the pin 31 further out of the cassette this positions the tip 47 of the pin 31 reliably inside the attenuation and retraction device the attenuation and retraction device begins to interact with the pin and the arrangement finally reaches the position shown in fig7 where the door is shut note that the pin is now in a relatively extended position as compared with fig6 a fig8 14 present functionalities in a wheel cassette 63 the cassette 63 may be built as a generally flat box which provides features allowing the cassette to be mounted on the door and supports the included components the cassette has a wheel holder 65 which extends out of the interior of the cassette 63 as shown in fig8 the wheel holder 65 is pivotably attached to the cassette 63 at a wheel holder pivot 67 axis where it is suspended between the side walls of the cassette 63 a torsional spring 69 urges the wheel holder 65 counter clockwise as shown in fig9 towards its most extended position thereby urging the wheel 33 towards the rail that would be placed above the cassette shown in.