I have tried this on the common plane of two solid objects, between a solid object and wireframe, and betwen wireframes only but the joining lines always show through. It seems to hide everything underneath (when wireframe) as expected but the line betwen the two objects keeps showing through. Example with two solids: if I draw two solids and join them end to end and creaate a 3d face over one plain, the adjoining lines still show through, same if one is a soild and one is a wireframe. Anyway, I hope I explained this well enough to get a solution.
Thanks in advance, Geo