AutoCad :: Viewport Set At 2D Wireframe

With my viewport set at "2D wireframe", all object lines show regardless of elevation which can make it difficult to read and hard to really get the idea of what is going on in the drawing. Therefore I changed my viewport to "hidden" in an attempt to depict what is higher in elevation over lower objects by having the higher objects cancel out lower objects when running over them. For some reason it works with conduit running over conduit but when the conduit runs over other objects (that are lower in elevation) created with the box command the lines do not get broken.. the lower box object actual cancels out the higher conduit object??