How to make area that player can not build ?

Hello!
I was using to mutator-zone-device to make not buildable zone but when I go outside the area and look inside of area , I acutually can build.
How can I make completely not buildable zone?

@Messiah4213 Thank you for your report! Can you please re-post using the “New Issue” option on the Issues and Bug Reporting forums? Posts with this feature are connected directly into our development team so we can quickly get to them!

For more information, such as how to get the reference ID, please check out the article here: Using the Creative and UEFN Bug Reporting Form

Now how did you fix it? @Messiah4213. I have the same problem, and I can’t find an object that ‘blocks’ buildings in itself. Like a typical FTN rock. @Stevie-Moon