The HZ / Stas zipper hook is a beautifully designed hook, there is an internal cam mechanism that means it grips the hangers as soon as you let go of the button on the side. Also due to this cam mechanism the more weight you add to the hook, the tighter it grips.

The hook itself holds 10kgs on the nylon / perlon hanger or up to 15 kgs on a steel hanger, this weight restriction is of course doubled when you are using two hooks per picture.

For a majority of pictures this will be a great choice, easy to use and adjust by the millimeter.