+----------------------------+
|  +----------------------+  |
|  | blah blah blah       |  |
|  +----------------------+  |
|                            |
|  +----------------------+  |
|  | asdf fdsa            |  |
|  | asdfear aoeirhaleir  |  |
|  +----------------------+  |
+----------------------------+

UIView rootView
  UIView containerView
    UILabel topLabel
    UILabel bottomLabel

|[topLabel]|
|[bottomLabel]|
V:|[topLabel][bottomLabel]|
|-[containerView]-|
[NSLayoutConstraint constraintWithFirstItem:containerView firstAttribute:NSLayoutConstraintAttributeCenterY relation:NSLayoutRelationEquals secondItem:rootView secondAttribute:NSLayoutConstraintAttributeCenterY multiplier:1 constant:0]