The Construction Standard > Bottoms page of the Catalog/Drawing Properties are where the bottom of the cabinets are set.
The Raise Bottom Inside Cabinet option is available for Floor, Wall and Tall cabinets.
In this example, the doors and kickboard have been removed and the Bottom has been raised 100mm.
An underpanel is basically a second bottom placed beneath the carcass bottom and made of panel material.
The height of the cabinet off the benchtop is affected, if not included, as the overall cabinet ends up closer to the benchtop. It is often the case that the underpanel on a number of adjoining cabinets is one piece and so placed on one and extended left/right to cover the others.
Edging of the underpanel can be controlled using the Edge checkboxes provided. The default is edging applied to the Front.
Machining holes can be controlled using the Back, Left End or Right End checkboxes.