Select Edit > Break All Intersections to break all segments where they intersect with other segments (where objects cross each other). 

This displays four lines that intersect and cross over each other. In order to edit the portions of this design, we will need to break the intersections.

Select Edit > Break All Intersections.

The intersecting lines have been broken into twelve separate lines. 

You can see from the blue dots that mark the end points, that we can now delete individual section of this design.  

Now the individual lines can be deleted and other lines can be added to create new shapes.

Alternatively, use the Break button to break only the selected intersections.

This allows you to manually select which intersections to break.