The Flat Pattern feature is intended to be used on drawings and for export to Sheet metal manufacturing.
The Flat Solid is inteded to be used....
It is used by NX as a means to produce the flat pattern, with bendfactor compensation.
Flat Solid also allows the user to create a so-called 'in process' model that lets you temporarily flatten a solid sheet-metal model so that you can add features, such as holes and cutouts, which will be created before the sheet metal blank is formed into the shape of the final model.
John is almost correct there,
In case one wants to add features in flat state, the feature is "Unbend" and "Rebend", not Flat Solid.
Flat Solid can though be used to show "in process" stages. I did not think of that.
And now with NX12 released, flat pattern and flat solid can be fixed at timestamp so can be placed anywhere in the feature history - even multiple flat pattern features can be created.
This further supports the staged approach.
Dave