Merges adjacent faces into a single face.

Button
Ribbon: Mesh tab
Mesh
Edit panel
Merge
FaceNot available on the ribbon
in the current workspace
Menu: Modify
Mesh
Editing
Merge
FaceNot available in menus
in the current workspaceYou can merge two or more adjacent mesh faces to form a single face.

The merge operation is performed only on mesh faces that are adjacent. Other types of subobjects are removed from the selection set.
Merging mesh faces that wrap a corner can have unintended results when you try to edit the mesh or convert it to other types of solid objects. For example, the mesh might no longer be watertight. For best results, restrict mesh merging to faces that are on the same plane.