You can edit the geometry of a selected part by dragging the shape handles on planar faces. 
 When you create parts from the layers of a wall or other host element, you can use this technique to prepare a view that effectively shows the composition of the various layers. 
 
Shape handles for parts do not display by default. Use the following procedure to display them for editing part geometry. 
- In the drawing area, select the part whose geometry you want to edit. 
- On the Properties palette, under Identity Data, select the Show Shape Handles option. 
- Drag the shape handles on planar faces to edit part geometry as needed. 
  Note: Any changes you make to the geometry of a part will not be retained by the original element if any of the parts derived from it are subsequently deleted.