Sluice gate gear
One of the silliest things about the Grand Canal, Dublin, is that it is so little used. A long time ago it was in constant use by barges bringing freight, including Guinness, and passengers across Ireland to the River Shannon. The last cargo barge used the canal in 1960. Now there are very few boats. I did see a couple yesterday when I took this - one moored properly and the other moored under a road bridge at the other side of the lock behind me.
I think the rusty thing is used for opening and closing the sluices in the lock gates.
More details about the canal - en.wikipedia.org/wiki/Grand_Canal_%28Ireland%29