Thanks for your reply, guys 'n gals.

I was not looking for the arcs you showed in your screenshots, @GunsForBucks, but somebody tilted the regular 2x1 stone bars so that they form an arch.

I guess I won't be able to do that then, as I intend to play without mods.

Thanks again for your help.

Edit: I also wished for that the developers would add the vertical tilt, @TehJumpingJawa