To cross a stream, road or valley (where the delay attributable to a flight of locks at either facet could well be unacceptable) the valley is usually spanned by a navigable aqueduct – a well known illustration in Wales would be the Pontcysyllte Aqueduct (now a UNESCO Environment Heritage https://devinakquz.wssblogs.com/36997754/5-essential-elements-for-musica-infantil