In order to understand Part Maker, you need to understand that in GHS we literally build a model of the vessel, and base all calculations on the model - not on intermediate abstractions such as Bonjean Curves. This is true not just of the hull(s) but also of the tanks, compartments, appendages - everything which contributes to the buoyancy or windage.
Of course, we are speaking of a mathematical model comprised of numbers; but the effect is very much like that of a physical model. You can view the model from various angles and manipulate its individual Parts.
What is a Part? Just those things which you want to handle when doing stability work. Each tank, for example, would be a Part; and obviously the hull would be a Part. Normally, the hulls of a multi-hull vessel would all be put into one Part, since there is usually no need to see their separate hydrostatic properties. But a ship in a dry dock would typically be a separate Part from the dry dock hull.
Still, Parts can be quite complex - such as a hull with several appendages. So GHS allows you to build your Parts from pieces called Components.
Take the case of a thruster tunnel. It not only modifies the hull, being a "negative appendage", but it probably modifies one or more tanks also. If you have ever manually constructed stations in the way of a thruster tunnel because the tunnel indentation had to be integral with the hull shape, you will love Part Maker. It not only constructs the cylindrical tunnel with one simple command but it fits the tunnel to the hull and will even fit tanks around the tunnel!
In short, Components allow you to build complex Parts accurately and quickly without causing unnecessary detail to clutter the reports.
Part Maker is a solid modeling tool designed specifically for hydrostatics models. It makes tanks, compartments, appendages, sponsons, camber, shell, insulation and fits them all together. It can scale, shift, stretch, combine, and display models.
Part Maker essentially extends the GHS command language so that the construction of a model can be described. Just as important as the final model itself is your expression of how you build the model; and this you can preserve for future reference. We call it the Run File. If you want to change the model in any way, simply edit your Run File and run Part Maker again.
Because it gives you so much power, we consider Part Maker to be an essential
part of GHS. Rowing is fine if you have the time. But if you want to get
there fast, you need a motor and you need Part Maker.