Centre of Mass
We can think of the weight of an object as if it acts at a single point. This point is called the centre of mass (or the centre of gravity) of the object.
The centre of mass of an object is where its mass may be thought to be concentrated.
In symmetrical objects, the centre of mass is along it's axis of symmetry. If an object has more than one axis of symmetry, its centre of mass is where they meet.