How does it work?

I sometimes think I should have been an engineer. I am fascinated by structures and many machines, and love to know how things work. Hence, seeing this on the way to the train today, I took a pic. Feel a bit sorry for the guy actually doing the work though, as his mate doesn't seem to be working too hard. But at least now I know what an escalator looks like before it is fitted. It reminded me of the most interesting bit of a tour of Oxford I did last year with the world's grumpiest tour guide (the weather was not good and there were only three people on his tour, of whom two spent half their time trying to get good photos of things!), where we happened upon the process of installing a new organ in Lincoln College Chapel - see here. For more info read the comment below the pic. I'd never really thought about how and when you would tune an organ!