Extra Edges Tool
The Extra Edges
tool is an alternative for merging faces that are tangent or nearly tangent. Instead of
merging two faces by selecting the faces, you select and remove the edge(s) between
faces to merge the faces. You should only merge faces that are tangent or close to
tangent. Otherwise, the results may be unexpected.
Note: Merging faces is recommended only as preparation for analysis. Merging faces simplifies the model but it may make it more difficult to modify.

This is one of a few geometry repair and navigation tools included here for ease of access. Their behavior is the same as if accessed from the Repair ribbon.