The single pit is one of the most widely used sanitation technologies. Excreta, along with anal cleansing materials (water or solids) are deposited into a pit. Lining the pit prevents it from collapsing and provides support to the superstructure. A single pit latrine consists of a toilet superstructures and a single pit to be filled up, emptied and filled up again. To improve pit latrines, aeration or an additional pit can be added (see single VIP, double VIP or double pit latrine).