(ii) The keys of the cell shall never be entrusted to a prisoner or convict officer. The lock and bolt of every cell shall be examined daily by the head warder responsible for lock-up. Only one occupant in each cell: Exception: Rule633. Every prisoner shall occupy a cell by himself by night, unless for medical or other special reasons it is necessary for prisoners to be associated. In such cases no fewer than three prisoners may be lodged in one cell, and each shall be supplied with separate bedding. Prison servants may enter a cell: Rule634. A prison servant may be permitted to enter a cell when his services are required there and he is accompanied by a warder. Labour in cell: Rule635. (i) The forms of labour selected for cells shall, as far as possible be such as will not facilitate escape or suicide. If it is necessary to employ prisoners on other tasks, special precautions shall be taken. (ii) Grinding mills provided in cells shall be fixed on cement platforms into which the lower stones should be embedded. Such cells shall not be used for night confinement, but only used during day for these prisoners awarded grinding as a prison punishment. Electric light in cells: Rule636. Every cell in a prison shall be provided with electric light at night. Electric fans may also be installed during summer where practicable. Drinking water in cells: Rule637. Prisoners confined in cells shall be provided with earthen pitchers or storing water for drinking. 218