# 2.4. Mesh Quality

    BEGIN MESH QUALITY
      CHECK MESH TOPOLOGY = <string>ON|OFF(ON)
    END [MESH QUALITY]

The `BEGIN MESH QUALITY` command block occurs within the region scope. This block will eventually offer a variety of options for diagnosing the quality and validity of the input mesh. Currently, the only option is CHECK MESH TOPOLOGY.

The `CHECK MESH TOPOLOGY` option checks for valid solid element connectivity and topology. In particular, it checks if any 3D bulk element is repeated twice in the mesh and if there are multiple elements which are (nonphysically) attached to the same side of one face.

This check is on by default, any errors found trigger a fatal error and abort the run. The check can be manually turned off by included the command block with the `OFF` option.