You can design a hull piece by piece, merging the parts at a later stage.
This is particularly useful in applications such as when you want to create
a hull bottom, sides and deck which are separately fair.
The simple example at right shows a hull and deck designed separately, then merged to create a single design incorporating both.
To help you to design the surfaces, you can work on one hull design, while keeping another design in memory as a reference. The view in the upper case at right was generated while the hull was being edited, with the deck held as such a reference "overlay".