A hook is where the pattern looks kinda like a hook. The one on the mojave closeup is a very good example of it.
I have heard that hooks can be a marker for a snake being a "het".
If you look at the other photos, they are all proven morphs that have s uper form so they could be called hets.
The female I posted first is a 100% het. I know since I produced her
and she also has a hook.
I think it's curious that a lot of co-dom morphs and some hets I have seen all seem to have some type of hook in their pattern.