All surface edges must be topologically matched before the geometry meets the requirements of topologically described geometry in a CAD system.
Edges fail to match because of a mismatch in the topology of two or more adjacent faces, or because the maximum distance between two adjacent edges is greater than the current accuracy defined in the CAD system. There may be a gap existing between the adjacent surface edges, or the edges may overlap to the extent that they can not be stitched.
