They were assigned jobs that basically kept the concentration camp functioning.
1. Some cleaned the barracks, the guards' houses, the hospital, and the kitchen.
2. Some cut and hauled wood for the stoves.
3. Some built more barracks for the newcomers and more privies or toilets.
4. Most of the workeers were used in the sorting sheds.
"....stacking the clothing and suitcases and possessions stolen from the prisoners, dividing them into piles to be sent back to Germany." (pg 125)
5. Hannah, Rivka, and Shifre worked in the kitchen.
"...hauling water in large buckets from the pump, spooning out the meager meals, washing the giant cauldrons in which the soup cooked, scrubbing the walls and floors." (pg 125)
6. When the four girls are stopped by the Nazi soldier at the end of the book and three of them are "chosen" by him to complete the load to Lilith's Cave, Rachel was at the pump because she was getting water for the women in the sewing shop. So, there was a sewing shop also.