sandbag

thumb|300px|Residents and volunteers work to fill sandbags during the Great Flood of 1993|Mississippi and Missouri river floods of 1993. thumb|300px|Members of the Georgia National Guard filling sandbags in preparation for floods.

A sandbag or dirtbag is a bag or sack made of hessian (burlap), polypropylene or other sturdy materials that is filled with sand or soil and used for such purposes as flood control, military fortification in trenches and bunkers, shielding glass windows in war zones, ballast, counterweight, and in other applications requiring mobile fortification, such as adding improvised additional protection to armored vehicles or tanks.