Free Throw Position question

[Terrapins Fan]

I had a friend ask me the other day about a FT position question. I didn't know the rule, but here's the situation.

Players line up for a FT as normal. Some players put their hands into the lane area, but they keep their feet in the spaces. Legal? Overall, I say yes. If they are slapping at one another, I'd tell them to knock it off. Can they put their hands in the lane?

After that, if they can, could they put a foot in the air into the lanes spaces? Why not? Where's the rule? That's the problem I am having. I need the rule for why they can not put their foot, while in the air over the line.

I imagine, there is something in the rules about breaking the plane. I just didn't see it. I read rule 8.