A block is usually caused by the body and hands being way in front and the club being under plane, you could swing left of left and still block the ball if you hold of the club leave it under plane and the face open obviously whereas...
a push is really just caused by swinging too far to the right and having the face square or slightly open to your swingpath,
nice comparison of Trevino and Couples
Tiger is blocking his tee shots right now, a lot of people would say he's "jammed up", which is a somewhat decent way to describe how the body gets when you block the ball, although as Brian touched on in his blog, it really has a lot to do with the club getting below the plane that you are swinging on whether it be shoulder or elbow.
Tiger swings down on the shoulder plane and then drops the club to the elbow plane which is below the the one he started on and tries to swing left to keep the ball from going right which puts his body way in front and abrah kadabrah some lady in the right gallerie just got a concussion.