The Boolean modifier on Difference to "open" an object

[Vince_EnVacances]

Hello guys.
I ran in a small problem. When I try to open a doorway (aka from the base of the wall) with the Boolean modifier it does not work properly.

In fact, it does nothing at all !

But if I move my “hole” object just a few pixels up from the base, it works.

What am I doing wrong ?
Also, do you know a better way to create arch doorways/windows ?

[Vince_EnVacances]

hooooo … doing the screenshots for this post, I just realized that if I stretch my “hole” object down and OUT of my wall, it works and opens the bottom of my wall

Hope it helps someone someday