Split Tool
Modify > Split Tool
 

Description:

      The Split Tool (Modify > Split Tool) allows you to interactively split faces or edges of an object by positioning one vertex at a time on its edges or faces.  To split an edge or a face, click first where you want the split to occur on an edge- you can hold down the mouse button and drag the new vertex to either endpoint of the edge in order to merge it with the vertex at that endpoint.  To split only an edge and none of the adjacent faces, press Enter.  Otherwise you can click and drag inside an adjacent face to draw out a splitting path, and click on another edge of the face to complete the split.  You can split several faces in succession with this method, drawing out a split along the surface.  Press Enter to finish a particular split sequence, and press Enter again to exit the tool.  You can press Delete to remove the last point you've placed in a multi-point split.
    To embed a polygon into another (after which the inside polygon can be deleted to create a hole), start your split on the interior of a polygon (rather than an edge) and draw out the interior polygon, pressing Enter when your done.  Press Enter again to exit the tool when you are done with it.  You can also right-click to exit this tool.


Notes:

- If you are splitting a subdivided shape, the subdivision will be updated each time you press Enter.