So - to open a can how does it work?

My thought is that you stick the point in the middle of the top, then adjust the sliding 'knife' to the can size, plunge it through, then work it around the rim. Seems like it would take a bit of physical strength!

Most hand operated can openers I've seen give you a 'leverage' mechanical advantage.

One we have [designed for arthritics or other lack of strength] uses a handle that works up and down, on a ratchet that drives the cutting wheel around the rim of the can. I reckon its great, but wifey does not seem to manage to get it going.