Sites is best suited (but not restricted) to the situation where an ecoregion has been divided into a set of candidate sites, called “planning units” that completely fill the region and are of roughly the same size and shape. Examples include regular grids, watersheds, landscapes, or any other geographic features that make sense from data compilation and conservation planning perspectives. These are the basic building blocks for assembling a portfolio. Therefore the delineation of planning units should be made carefully. There are several different files that are used to characterize the planning units.