Making floor invisible.

Hope someone may know the answer, to something which may be simple.

I have created a sphere in 3d max with flipped normals and a spherical map applied to it. I have my Vr Pawn on a box brush with a NavMesh applied.
All I want to do is be able to look around within the sphere which is fine. My main question is can you make a box brush with a NavMesh invisible so there is nothing obstructing the view of the Pawn in Vr?


Was being a bit thick! An invisible materiel sorted it.