The Borrow/Fill Area tools create an area that can be used for cut/fill if the site grading optimization needs to cut or fill. OpenSite Designer automated grading optimization manipulates all site objects, respective of their grading settings, to do all grading operations within the site Limits of Disturbance and within the limits of disturbance of the proposed objects. This sometimes does not produce the desired grading results. Large open spaces can be ignored, and objects raised/lowered to elevations that do not reflect desired results. The Borrow/Fill areas allow you to influence the optimization to create the desired result.