sentences:  The bottom of each lock was connected by a culvert to the bottom of its pond, and a paddle controlled the flow of water through the culvert.The paddle had to be capable of sealing the culvert against flow in either direction, since when closed it had to prevent the lock from emptying when it is full, and from filling when it is empty.British Waterways, in conjunction with the Macclesfield Canal Society, are hoping to restore one of the side ponds to enable its operation to be demonstrated, although it is likely that it will only be used for demonstrations, rather than in normal operation of the lock.