(1) A standing sentry at police stations shall ordinarily not be posted, but at night one of the constables sleeping at the station shall be told off by the station clerk or senior officer present to sleep in front of the door of the police station which shall be securely fastened. (2) In cases where the lock-up contains prisoners, or there is valuable property in the store-room [vide rule 22.18(1)] or animals in the cattle- pound, there shall be a constable on watch, who shall be posted with special regard to the protection of lock-up, the store- room or the cattle pound, as the case may be, and he shall be responsible for its safe custody. Standing orders describing the duties of the sentry in regard to the protection of each of these three places shall be framed by the Superintendent of Police and hung up in the police station office. The officer in charge of the police station shall read out the appropriate part or parts of this standing order when allocating duties at roll call (vide rule 22.11). If the subsequent arrival of prisoners, valuable property or cattle necessitates an extension of the duties detailed at roll call, the station clerk shall inform the constables concerned, shall read out to them the standing order applicable and shall obtain their sig- natures or thumb-impressions in the station diary. (3) Ordinarily there shall be a police officer, who shall usually be the senior police officer present at the station house, available and ready in proper uniform to receive information and complaints and to afford such assistance as may be lawful and necessary; and at every post there shall be at all times one police officer in uniform in charge of the building and property, but such police officer shall not be expected to do more than keep on the alert.