Every bicycle left here overnight must carry a registration sticker. The sticker is free, takes four minutes at the porters' lodge, and needs the frame number, which is usually stamped under the pedals. An unregistered bicycle is not removed and is not fined. What happens instead is that we cannot return it. Two thirds of the machines recovered by the police last year sat in a store for six months and were then sold, because nothing on them said whose they were. The sticker is tied to you and not to the bicycle. If you sell the bicycle, tell the lodge, or the next owner will be recorded as a thief the first time it is checked.