Bridgewater canal - Cheshire

Another bike ride along the canals
This bit is part of the Bridgewater canal and is part of the Cheshire loop.
One of the unusual thing about this is the lack of locks - the whole area is flat so the canal doesn't need to go up or down at all.
A previous shot shows a sort of crane thing. These are places along the canal along with some long square pieces of woods - just a bit longer than the canal is wide.
A close look shows a small slot in the canal walls nearby.
If the canal springs a leak (insert vegetable and Welsh person based joke here!) then the crane is used to lower the wood into the slots to dam up the canal and stop the whole things from draining.
I'm not sure when this started to be done - but I know it was at least extended during WW2 because the canals played a big part in transporting good around the country - and they were rather vulnerable to bombers from the EU - sorry Germany I been watching Brexit stuff too much! - so this system was to be employed if canal walls or lock gates were attacked.
You often see the same system employed near lock gates.

You see - reading my stuff learns you something!!