Check integrity script renamed to Select non-manifold edges
I thought this would be clearer and bette rinserted. The script can be found here:
It is found in the Mesh menu in Edit mode, inside the Edges submenu. Simply run the script, and non-manifold edges, if any, will be selected, so you can easily find and fix them. Basically this script's main use if to see if a mesh can be converted to a solid when imported in a program able to do so.
The script's wiki page is at http://wiki.blender.org/index.php?title=Extensions:2.5/Py/Scripts/Modeling/Select_nonmanifold_edges
Note: I just discovered that blender already features a built-in command to do that: Ctrl + Alt + Shift + m, which makes this script totally obosolete now!