Slab Edge Extra Line...Help Please

I have created a foundation slab with a slab edge in revit structure 2010, in a section of this edge at a coarse detail level it is just how I want it, but in medium and fine detail level there is a line that shows between the slab and the slab edge, how do I stop display of this line in these detail levels

Thanks in advance
Graham

Sorted this

the material for the slab and the slab edge had to be identical for the line to dissapear