How to get the Collider point?

Two Box(added Box Collider already) hit each other,
and How can I get the point where they hit?
They may hit at an area,but can I get the center point of the area?

In OnCollisionEnter, you get a Collision passed as a parameter, from which you can query the contact points:

function OnCollisionEnter(collision : Collision) {
    for (var contact : ContactPoint in collision.contacts) {
        Debug.Log(contact.point);
    }
}