Thanks bdfd, but I can't construct a wall at the side of the stairs, just to close the gap.

I'm just looking for a possibility to design a wall with an skewed end of approx 35 degrees (not 90 degrees as the default wall-ends). Or if you want, a wall with the inside longer than the outside.

Pls have a look at the picture to see my case :

https://www.mediafire.com/?2t9bh9a8759p6qu[/img]
Is this not possible ?

Thank you very much for your input.

Benno