 The Nazis operated several categories of "Arbeitslager" for different categories of inmates.The largest number of them held civilians forcibly abducted in the occupied countries (see Łapanka for Polish context) to provide labour in the German war industry, repair bombed railroads and bridges, or work on farms and in stone quarries.The Nazis also operated concentration camps, some of which provided free forced labor for industrial and other jobs while others existed purely for the extermination of their inmates.