Checking Model Geometry
By default, each time you add or modify a feature, the feature is checked
against any adjacent faces and edges. To increase the level of error checking,
turn on the Verification on rebuild
option. When this option is turned on, the software checks every new or
changed feature against all existing faces and edges, not just adjacent
faces and edges. Features that cause invalid geometry fail when this option
is turned on.
This option has a negative effect on performance.
Rebuilding the model is considerably slower and more CPU-intensive. This
option applies to all documents, not just the active document. Use this
option only when needed, then be sure to turn it off when you are done.
To verify the model with a higher level
of error checking:
Click Options
on the Standard toolbar, or click Tools,
Options.
On the System
Options tab, select Performance.
Select Verification
on rebuild, then click OK.
-
Press Ctrl + Q
to regenerate the entire model.
When you press Ctrl
+ Q, it causes a complete rebuild of all the features in the model.
The Edit, Rebuild 
operation (Ctrl + B)
only rebuilds new or changed features and their children.
Examine and correct any features that fail, beginning
with the first failed feature in the FeatureManager design tree. Often
fixing one failed feature allows subsequent failed features to rebuild
successfully.
When you are satisfied that all the errors are
corrected, repeat steps 1 and 2, clear Verification
on rebuild, then click OK.