On 17 Aug, 10:01, robgraham wrote:
This has nothing to do with DIY, but takes advantage of the
encyclopaedic knowledge here !

I've a troublesome knee and have been banned from all physical DIY by
the physio - light exercises and 1 hour's flat walk a day. *That's
where the canal comes in - I'm exploring the local canal (near
Edinburgh) in 1 1/2 mile sections. *The mind as you can well imagine
goes into neutral and the question arose as to how barges crossed in
the old days when there was only one path for the horse and draw
rope? *Anyone know ?

Rob

I believe the tow ropes were wieghted so they sank so permitting a
boat to pass over them if the rope was allowed to slacken.. At canal
tunnels, boats were "legged through by professional teams who lay on
legging planks and walked the boats through by pushing with their
feet.
http://en.wikipedia.org/wiki/Legging_(canals)