This video will show you how to find and fix Overlapping, or Coincident, Vertices in Maya.
Overlapping vertices are separate, individual vertices in a single 3D object that occupy the same location. Coincident vertices can cause smoothing problems when the model is rendered, and can cause errors when the model is exported to other applications.
CheckMate Pro Specification: support.turbosquid.com/entries/20203606-checkmate-pro-specification
Coincident Vertices: support.turbosquid.com/entries/20213136
CheckMate Tools: support.turbosquid.com/entries/20252981
CheckMate Scripts: turbosquid.com/CheckMateTools/