What is the award?

It depends on the rules and when the base is blocked and by how much.

So for pro, if the play is eminent (e.g. the throw has been released) at the time the runner was hindered its legal.

For college, you cant drop the knee until the throw is caught or its obstruction and a minimum one base award.

And finally for HS, you cant completely block the base until you have the ball or its obstruction and a minimum one base award.  If you give partial access even if its not the part the runner wants its legal.

Not completely true.  In a ruling, Eliot Hopkins has said the the runner must have access to a portion of  the edge of the base facing him.  In other words, the defense cannot claim the runner had access to the back side of the back when blocking the entire front side.

Correct and what I meant - Ive never had anyone try to claim access to any side but the side the runner was on but now that you mention it I can see someone trying to do so.  Id try hard not to laugh when I dealt with that line of so called reasoning.

Thanks guys

I've never even once seen it called.

Not in games that I've coached.  Or spectated. Or watched on TV.

That's because it happens much less than it used to because it is illegal in LL,Fed, and NCAA, degrees vary, but they have strengthened the obstruction rules to  eliminate this action. By the time they get the MLB, where they can, it isn't part of their game so they don't.