keeping an object's balance, when the line of action through the centre of gravity of the object lies within its base, there is a clockwise moment about point A due to its weight, the line of action is still in the base of the object, thus the object will not topple, however, when the line of action through the centre of gravity of the object lies outside the base, there is an anticlockwise moment about point A due to its weight, thus the object will topple