Combining Two or More Vertices by Individual Selection

Click the Select the anchor vertex tool guide. The cursor changes to select the anchor vertex (kept vertex) to which merged vertices are pulled.
Select your desired anchor vertex. The anchor vertex is highlighted and the cursor changes to Select the vertex to be released.

Note: The anchor vertex remains highlighted until you escape out of the command or click Select the anchor vertex again to deselect the first vertex and initiate another sequence.
Select a vertex to be merged. The anchor vertex is retained and the second selection is removed. The block structure is modified to fit the remaining vertices.

Note: The cursor remains in Select the vertex to be released mode allowing multiple vertices to be combined with the anchor vertex until you escape out of the command, or click white space, or click Select the anchor vertex again to initiate a new sequence.

Note: Both vertices must be in the same component. If you attempt to merge vertices from separate parts, bodies, or components, an error message will be generated.

When merging vertices by individual selection, you can modify the behavior using the Merge Options panel:

Enable Merge to Average. The resulting vertex will be placed at the midpoint between the anchor vertex and the second vertex.
Enable Propagate Merge. Parallel edges of all connected, mapped faces will be collapsed irrespective of the block type. Some blocking associations may be lost and will have to be reset. For example, when edges spanning multiple curves are collapsed, a new composite group of edges will have to be created. By default, Propagate Merge is disabled. Combining a single pair of vertices on a mapped face may result in a degenerate face depending on the type of volume block.