SS Major Bernhard Krüger replaced Naujocks; searching through the offices used daily by Operation Andreas, he found the copper engraving plates and the machinery, although some of the wire gauzes used to make the watermarks were bent.[40] He was ordered to use the Jewish prisoners incarcerated in the Nazi concentration camps,[18] and set up his unit in blocks 18 and 19 at Sachsenhausen. The blocks were isolated from the rest of the camp by additional barbed wire fences, and a SS-Totenkopfverbände unit was assigned as guards.[41]