To cross a stream, road or valley (where the hold off because of a flight of locks at either facet might be unacceptable) the valley is usually spanned by a navigable aqueduct – a popular example in Wales would be the Pontcysyllte Aqueduct (now a UNESCO Earth Heritage Website) https://chancezejpt.activablog.com/36290632/the-2-minute-rule-for-urso-fofo