Life on the short side

Take a look at the position below. Black to move, with a chance for discovered check.  Can he win this?  If he can, what is the winning idea?

Can White hold the draw with best play?  How?

When I first looked at this position, I figured that Black wins this by getting his Rook to the g-file and cutting off white's King.  Something like this.

That doesn't work.  Let's try another idea.  Maybe the discovered check gets somewhere.

 So, is this a win for Black?  Not really.  The continuation I showed wasn't accurate and White missed a resource. White's 3rd move above was an error.  Can you find the right idea?

Take credit for yourself if you wanted to play the Rook to c8, as that also holds the draw.

Introducing the Goal Line Stand

Here is now a glimpse of the inner workings of this drawing idea with the analysis below.  Pay special attention to the defense of the first rank and how this makes the draw possible.

This is an illustration of the importance of the so-called "short side" of the board in Rook and Pawn endings.  Whether you are defending or trying to win, your chances are best if your King is on the short side.