Using QGIS' Reshape Features command to edit polygons

I found the Reshape Features command in QGIS useful to manipulate the shape of polygons. The command can add to or subtract from the shape of the polygon depending on the location of the first and last vertices placed with the command. The following examples illustrate this.

To subtract from the shape of the polygon

1. Select a polygon layer, e.g. waterbody. Select Layer | Toggle Editing.
   
   The layer is selected for editing.
   
2. In the Advanced Editing tool bar, select the Reshape Features icon.
3. In the map view, click on one point outside the polygon (point 1). Click on one or more points inside the polygon (point 2... point 3). Click on a point outside the polygon (point 4).
   
   
4. Press the mouse right button to complete the action.
   
   The newly digitized polygon is subtracted from the original polygon.
   

To add to the polygon shape

1. Select a polygon layer, e.g. waterbody. Select Layer | Toggle Editing.
   
   The layer is selected for editing.
2. In the Advanced Editing tool bar, select the Reshape Features icon.
3. In the Map view, click on one point inside the polygon (point 1). Click on one or more points outside the polygon (point 2...point 3). Click on a point inside the polygon (point 4).
   
   
4. Press the mouse right button to complete the action.
   
   The newly digitized polygon is added to the original polygon.