Command entry:Select an Edit Poly or editable poly object. 
Modify panel Vertex/Edge/Border sub-object level Edit Vertices/Edges/Borders rollout Chamfer 
(Settings)
Chamfering creates new faces around the chamfered entity, along with connecting edges. Or, with the Open option, you can create an open (empty) area instead. For vertices, edges, and borders, you can use the caddy to set the chamfer amount numerically and to toggle the Open option. The Segments setting applies only to edges and borders.
For details on using the caddy controls, see The Caddy Interface.
Chamfer Amount
Segments(edges/borders only) Adds edges and polygons over the area of the chamfer, and, with single chamfered edges, rounds off the chamfer. By default, the chamfer uses a single segment, which covers the chamfered area with a new polygon positioned diagonally with respect to the original corner. The higher the Segments value you use, the more the chamfer is rounded off.
If you chamfer two or more adjacent, open edges at a time, the rounding off takes place only at open ends of the edges. No rounding takes place where the edges meet.
Open
(Vertex), 
(Edge), or 
(Border) sub-object level 
(Chamfer) or choose Chamfer Settings from the drop-down list.
OK
Apply and Continue
Cancel