Cussane or Coosaun Lock was the lowest of three on the Killaloe Canal, which was the uppermost section of the Limerick Navigation. It was a double lock or “staircase pair”.
Cussane Lock (OSI ~1900)
You can see what the lockkeeper’s house looked like in 2015 in the article “A Flooded Landscape Revealed“, written by folk who surveyed the area last year for Irish Water.
Irish waterways history 