To cross a stream, road or valley (in which the delay a result of a flight of locks at possibly side 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 https://musica-infantil01099.blogadvize.com/45069090/5-essential-elements-for-musica-infantil