A prison cell or holding cell or lock-up is a small room in a prison, or police station where a prisoner is held. Prison cells are usually about 6 by 8 feet in size with steel or brick walls and one solid or barred door that locks from the outside. Many modern prison cells are pre-cast. Solid doors may have a window that allows the prisoner to be observed from the outside. Furnishings and fixtures inside the cell are constructed so that they cannot be easily broken and are anchored to the walls or floor. Stainless steel lavatories and commodes are also used. This prevents vandalism or the making of weapons. There are a number of prison and prison cell configurations, from simple police station holding cells to massive cell blocks in larger correctional facilities. In the United Kingdom, cells in a police station are the responsibility of the Custody Sergeant, who also logs each detainee and allocates him or her an available cell. Custody Sergeants also ensure cells are clean and as germ-free as possible, in accordance with the Human Rights Act. The practice of assigning only one inmate to each cell in a prison is called single-celling. In the United States, the standard cell is equipped with either a ledge or a steel bedstead that holds a “mattress” (in actuality, more like a gymnasium floor mat). A one-piece sink/toilet constructed of welded, putatively stainless steel is also provided. Bars typify older jails, while newer ones have doors that typically feature a small safety glass window and, often, a metal flap that can be opened, e.g., to serve meals. Some United States prisons offer upgrades. Costing around 100 dollars a night, these cells are considered cleaner and quieter, and some of them offer extra facilities.