How to crop a mesh or merge layers
 

My objective is to create a 2 dimensional polyhedral mesh, the boundary being a square.
So far I have used Gmsh to create a 2 dimensional tetrahedral mesh (see link), and polyDualMesh to create a polyhedral mesh. But the last command also divided the mesh once in the third dimension, which is what I want to avoid.

Is there a way to merge these layers back together to get a proper 2 dimensional mesh?
Or can I throw away (crop) one of the two layers, also resulting in a proper 2 dimensional mesh?
Or is there a setting for polyDualMesh that will prevent it from dividing in the third dimension?

The answer can now be found on the OpenFoam wiki: http://openfoamwiki.net/index.php/Po...esh_generation