Anyway, I knew locks were devices for raising barges through hilly parts of a canal, but I thought each gate was a seperate lock. It turns out that, if I've understood correctly, both gates in conjunction with the narrow lock chamber form the complete lock. This page seems quite informative for anyone else not familiar with canals and their associated terminlogy:
http://en.wikipedia.org/wiki/Canal_lock
I now understand what Will was referring to when he mentioned "pound". Steve Grindlay did an absolutely brilliant job, last night, of explaining the other type of pound used for animals at the Horniman's Triangle, but I'll save that story for a different topic.
