OBButtonTray is a UIView subclass in OnBoardingKit.framework.
It can contain multiple buttons as well as a "caption label", a small UILabel usually reserved for legal text.
An instance of OBButtonTray is automatically created during the initialization of an OBWelcomeController and can be accessed from the latter.
Adding caption text
[buttonTray addCaptionText:@"This text is really small!"];