Thanks for the suggestion Andy. I didn't explain what I was after well enough though. This picture might help. It is the result of one runway mesh (with cut out middle) overlaid on top of another one. Most airports have multiple runways. I'd like to merge these two meshes into a single mesh, with no mesh going over the cut out middles but without losing the neat lines of the cut out edges.
Here's a rough attempt at vertex picking and removing mesh elements that overlap into the cut out middles, but doing this messes up the straight edges of the middles and I still have lots of overlapped mesh.
Finally if I merge the above meshes I lose my cut outs.
Is it possible? I'm looking to do something in a scripted way.
Phil