thanks Christophe Fortineau,
didn't checked because these are not referance layers. this view is second floor, and rail+stair is present on the first floor(and of course connecting to second floors base).
i wrote "slab is not transparent" because if it was, then bottom part would show(i mean the problem is not that it's transparent(because if slab would be transparent then rail would show in any case))
simply how can it present below the slab(invisible) for bottom end, and above the slab(visible) for upper end of the rail, in the 2D plan view.
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