Railing wall - Stairs

I want a solid railing wall right next to a staircase that has a railing of its own. Everytime i try to draw this solid railing wall, it always conforms to the slope of the stairs AND the stairs have a railing...too.

How can i draw a plain solid railing wall along side stairs without the wall changing it shape? Is there some kind of setting i can try?

I think you can put a wall next to the stairs, not under it, then look at the wall in a cross section. Click on the wall and you should see some handles that you can use to change the height and shape to conform as a solid wall next to the stairs.