To cross a stream, road or valley (where the delay attributable to a flight of locks at possibly facet could well be unacceptable) the valley is usually spanned by a navigable aqueduct – a famed illustration in Wales would be the Pontcysyllte Aqueduct (now a UNESCO Planet Heritage Web-site) https://sergiobhmtw.blogunok.com/37264709/helping-the-others-realize-the-advantages-of-urso-fofo