Select an Edit Poly or editable poly object. > Modify panel > Vertex/Edge/Border sub-object level > Edit Vertices/Edges/Borders
rollout > Extrude Settings button
Select an Edit Poly or editable poly object. > Vertex/Edge/Border sub-object level > Quad menu > tools 2 quadrant > Extrude
Settings button
Use this dialog for extruding vertices, edges, and borders in Interactive Manipulation mode.
Note: At the Border sub-object level, this dialog is named Extrude Edges.

Extrusion Height—Specifies the amount of the extrusion in scene units.
You can extrude sub-objects outward or inward, depending on whether the value is positive or negative.
Extrusion Base Width—Specifies the size of the extrusion base in scene units.
You can set this as high as you want, but the actual size cannot extend beyond the vertices adjacent to the extruded sub-object(s).