Vertices are points in space: They define the structure of other sub-objects that make up the poly object. When vertices are moved or edited, the geometry they form is affected as well. Vertices can also exist independently; such isolated vertices can be used to construct other geometry but are otherwise invisible when rendering.
At the Edit Poly (Vertex) sub-object level, you can select single and multiple vertices and move them using standard methods. This topic covers the Edit Vertices and Edit Geometry rollouts; for other controls, see Edit Poly Modifier.
You can use either of two methods to combine several vertices into one, also known as welding. If the vertices are very close together, use the Weld function. You can also use Weld to combine a number of vertices to the average position of all of them.
Alternatively, to combine two vertices that are far apart, resulting in a single vertex that's in the same position as one of them, use Target Weld.
If the vertices are very close together, simply click Weld. If they are farther apart, click 
(Settings) to the right of the Weld button. This opens the Weld Vertices caddy, where you can increase the Weld Threshold. Once you change Weld Threshold, it remains at the new value until you change
it again, or until the end of the 3ds Max session.
The two vertices must be contiguous; that is, they must be connected by a single edge.
See Edit Poly Mode rollout for information on the Edit Poly Mode rollout settings.
See Selection Rollout (Edit Poly Modifier) for information on the Selection rollout settings.
Soft Selection controls apply a smooth falloff between selected sub-objects and unselected ones. When Use Soft Selection is on, unselected sub-objects near your selection are given partial selection values. These values are shown in the viewports by means of a color gradient on the vertices, and optionally on the faces. They affect most types of sub-object deformations, such as the Move, Rotate, and Scale functions, as well as any deformation modifiers (such as Bend) applied to the object. This provides a magnet-like effect with a sphere of influence around the selection.
For more information, see Soft Selection Rollout.
This rollout includes commands specific to vertex editing.
Deletes selected vertices and combines the polygons that use them. The keyboard shortcut is Backspace.
Removing one or more vertices deletes them and retriangulates the mesh to keep the surface intact. If you use Delete instead, the polygons depending on those vertices are deleted as well, creating a hole in the mesh.
Lets you extrude vertices manually via direct manipulation in the viewport. Click this button, and then drag vertically on any vertex to extrude it.
Extruding a vertex moves it along a normal and creates new polygons that form the sides of the extrusion, connecting the vertex to the object. The extrusion has the same number of sides as the number of polygons that originally used the extruded vertex.
Following are important aspects of vertex extrusion:
Chamfer box showing extruded vertex
Extrude SettingsOpens the Extrude Vertices caddy, which lets you perform extrusion via interactive manipulation.
If you click this button after performing a manual extrusion, the same extrusion is performed on the current selection as a preview and the caddy opens with Extrusion Height set to the amount of the last manual extrusion.
Combines contiguous, selected vertices that fall within the tolerance specified in Weld Vertices caddy. All edges become connected to the resulting single vertex.
Weld is best suited to automatically simplifying geometry that has areas with a number of vertices that are very close together. Before using Weld, set the Weld Threshold via the Weld caddy. To weld vertices that are relatively far apart, use Target Weld instead.
Weld SettingsOpens the Weld Vertices caddy, which lets you specify the weld threshold.
Click this button and then drag vertices in the active object. To chamfer vertices numerically, click the Chamfer Settings button and use the Chamfer Amount value.
If you chamfer multiple selected vertices, all of them are chamfered identically. If you drag an unselected vertex, any selected vertices are first deselected.
Each chamfered vertex is effectively replaced by a new face that connects new points on all edges leading to the original vertex. These new points are exactly <chamfer amount> distance from the original vertex along each of these edges. New chamfer faces are created with the material ID of one of the neighboring faces (picked at random) and a smoothing group which is an intersection of all neighboring smoothing groups.
For example, if you chamfer one corner of a box, the single corner vertex is replaced by a triangular face whose vertices move along the three edges that led to the corner. Outside faces are rearranged and split to use these three new vertices, and a new triangle is created at the corner.
Alternatively, you can create open space around the chamfered vertices; for details, see Chamfer.
Chamfer SettingsOpens the Chamfer caddy, which lets you chamfer vertices via interactive manipulation and toggle the Open option.
If you click this button after performing a manual chamfer, the same chamfer is performed on the current selection as a preview and the caddy opens with Chamfer Amount set to the amount of the last manual chamfer.
Allows you to select a vertex and weld it to a neighboring target vertex. Target Weld works only with pairs of contiguous vertices; that is, vertices connected by a single edge.
In Target Weld mode, the mouse cursor, when positioned over a vertex, changes to a + cursor. Click and then move the mouse; a dashed, rubber-band line connects the vertex to the mouse cursor. Position the cursor over another, neighboring vertex and when the + cursor appears again, click the mouse. The first vertex moves to the position of the second and the two are welded. Target Weld remains active until you click the button again or right-click in the viewport.
Creates new edges between pairs of selected vertices.
Connect does not let the new edges cross. Thus, for example, if you select all four vertices of a four-sided polygon and then click Connect, only two of the vertices will be connected. In this case, to connect all four vertices with new edges, use Cut.
Certain modeling operations can leave unused (isolated) map vertices that show up in the Unwrap UVW editor, but cannot be used for mapping. You can use this button to automatically delete these map vertices.
Paint Deformation lets you stroke elevated and indented areas directly onto object surfaces. For more information, see Paint Deformation Rollout (Polymesh).
Modify panel 
