Flooding recalculates the pour areaand recreates all clearances forthe current obstacles within the pour outline,observing clearancerules. Hatchingrefills (with hatch lines) existing pourpolygons for thecurrent session; it does not recalculate the pour area. Eachtime youopen a design file, you must flood or hatchthe design; this informationis not saved. In most cases, you can simply Hatch. Use Flood if you makechanges to thecopper pour polygon that could create clearanceviolations or if you changeclearance rules.