it is a fiendishly clever mechanism using a column of ball bearings to drive a rack. It will work both ways - either pulling or pushing - and drives a shuttle around the cleat or ring, carrying with it whatever line you have tied to it. Can't be a really huge line, but can be a smaller one leading a larger one. The eye would go around a ring or line, or even a skinny cleat, but is too small for a bulky cleat.

The build quality is quite good. The action is slightly stiff, and so requires a bit of force that might disturb the thing being captured. I know of perhaps four or five devices begin sold to solve this problem, and own a couple of them. The advantage of the Hook & Moor is that you can hook and pull on a ring, which pulls it towards you by its action, even if it is a little stiff. Many of them require pushing, that it very likely to push the mooring ball or whatever away just as you are trying to capture it. The Hook & Moor end is kind of like a boat hook, so you can pull things towards you as you get it to work.