The main role for a Number 8 is simply to control the ball at the base of the scrum, whilst playing a role in driving the scrum forward. The key is to build up an understanding with the scrum-half in order to know when he wants the ball, when he doesn't. He needs to be able to carry the ball effecitvely at the base of the ruck and find a front foot carry so that the backs have a platform to play off. Hope this helps.

1/ To push like crazy 2/ To pick up and go forward if your scrum has a push on and set up a move 3/ To pick up and save the position if your scrum is going backwards.