Sorry for my bad english but I have a problem with mesh which I imported from blender to unreal engine. I created pool table in blender but when I import it in unreal the “walls” of my mesh disappear. how can I solve this problem? (one of these photos is a rendering from blender instead other one is result in unreal engine). Thanks a lot for your time 
Hi 753 Studio,
This would be caused by your normals being flipped and facing the wrong way.
You’ll need to correct this in your modeling application.
Thank you!
Tim