FIRST allows you to divide the first entity (excluding
circles) selected into two separate entities, based on
intersections with other entities. The current attribute
values are assigned to one or two of the entities.

Select an intersecting entity, near the intersection of 
the desired break. The original entity is redrawn as two
entities. The first portion of the selected entity (on the
side it was selected) is redrawn up to the intersection
point with the original attributes assigned. The second
portion of the entity is created as a separate entity, 
with current attribute settings.
