If you look carefully at the windows of the Yeshiva in Volozhin, you will notice something interesting:
The bars in the windows are all on an angle!
The reason for this may be that they didn’t want it to form a cross. There were many Tzadikim in Europe who we concerned about things like this. Of course, we cannot conclusively know that this was the reason behind it, but it is an interesting possibility.
In the Shull where the Holy Steipler Gaon used to davven, he instructed them to make the bars non-fully perpendicular on the windows for precisely this reason:
