Sandbags are a light, inexpensive, and, apart from fences, about as weak a defensive barrier as could be imagined. Sandbags could be used to keep troops and civilians from entering areas that they were not supposed to go to, whether because of traffic concerns (such as taking poorly-planned routes to resources) or of hazards. They can hold back infantry and light vehicles, but cannot block tank ordnance and any sort of explosive weapon, including grenades, tank shells, rockets, and artillery can eliminate a pile of sandbags with ease. However, this was counterbalanced by the sandbag's trivial expense - a base could be ringed in sandbags for half the price it would take to put in sturdy concrete walls. They were used by the Allies during the Second World War and continue to be an element of the Allied arsenal, and by GDI and Nod during the First Tiberium War. They also served a variety of civilian purposes and appear in Tiberian Sun and its expansion during the Second Tiberium War as part of the scenery on some skirmish maps, and as non-buildable defensive barrier in some single player missions (such as in the first GDI mission in Tiberian Sun), however, they can built in some mods.